A character, after delivering a Double Entendre, adds a remark to their statement to ensure that the audience spots the hidden meaning. Alternatively, after hearing somebody else deliver a double entendre, appends it for them to much the same effect.
Typical phrases used for this purpose include:
"...if you know what I mean." Which can be expanded with: "...and I think you do."
Maniwa: For women like her, who subconsciously act repressed, you have to have patience and delicacy. Like peeling a ripe apple.
Ikari: So you wanna peel her apple?
Maniwa: Ya'know, women hate dirty jokes.
Finbarr Saunders of the controversial "adult" comic Viz was a parody of this. He would react to any even marginally suggestive line with spluttered laughs (written 'Fnarr fnarr') eyeball rolling, nudges ('Eh? Eh?'), and silly catchphrases ('As the actress said to the bishop'), but would put innocent interpretations on the words of his mother and Mr Gimlet the lodger as they went off to have sex.
Mrs. S: How about a little shag, Mr Gimlet?
Mr. G: Righto, Mrs. Saunders, I'll just get me pipe out.
Finbarr assumes she's offering him some tobacco.
Those Lacking Spines, a Kingdom Hearts fanfic, uses the term "...you know" to describe a certain male body part the members of Organization XIII were in danger of losing... if you know what I mean.
In Shelter, Jeanne is concerned because her brother Zach has been surfing with Shaun, who's gay. She talks to Zach about it, saying: "I don't think that he's the best guy to be hanging out with all day half naked, if you know what I mean."
Loach: What happened to your nose, Gittes? Somebody slammed a bedroom window on it?
Jake: Nope. Your wife got excited. She crossed her legs a little too quick, you understand what I mean pal?.
Combines with That Came Out Wrong in F/X 2. Brian Dennehy's cop character is explaining to a female character how to use a pistol. His lesson ends with, "And that's how you cock the sucker..." (*he realizes what he's just said*) "...in a manner of speaking."
Played with in the Stanley Kubrick adaptation of Lolita. Humbert and Lolita turn up at a hotel and discover There Is Only One Bed. Claire Quilty overhears this and later corners Humbert with a long rambling conversation about his beautiful 'daughter' and how he'd love to have one like her, "you know what I mean". Humbert is unaware that Quilty is also a paedophile and so the conversation just leaves him disturbed and confused.
Oddly, since the author is American, in Gene Wolfe's Book of the New Sun, one character an android Jonas is fond of inserting "as x said to y" comments in his speech, although unlike most examples, they don't always have a bawdy connotation.
Justified Trope, in that this habit reveals an important point about his background.
Nanny Ogg quite often used double entendres (though, as the books note, hers were single entendres and proud of it.)
"Just twist the first thing you can grab", as the High Priest said to the vestal virgin.
Nanny Ogg's actions are occasionally described like this. For example, she often likes to sing about how fortunate the hedgehog is compared to an unbelievable number of other animals. While doing humorous gestures ...
It was a running gag that when Joey said something raunchy, he'd follow up with an explanation in case the others didn't catch his meaning, which they always did. Once he said, "If you know what I mean," to which Monica replied, "Joey? We always know what you mean."
In an earlier episode the Friends were comparing sex to a concert, comparing foreplay to a comedian, and penetration as the band. The women say that they should bring back the comedian for a second go a bit more often otherwise they might just end up listening to the album of the band instead. Joey responds with: "...We're still talking about sex, right?"
Chandler seeing Rachel's boss led to this exchange.
Chandler: She's not just the boss in your office...if you know what I mean.
Joey:(chuckles, then gets stared at) Sorry, I knew what he meant.
A game on Whose Line Is It Anyway?, using the original trope name, is devoted to these jokes. It features the performers turning every single line into a double entendre by ending every sentence with, "If you know what I mean." The game's comedic value comes from the players thinking up ever more elaborate metaphors, often going to the point where they don't make any sense eg. the infamous: "Can I help you fluff your Garfield?"
If you think that last one doesn't make any sense, try saying it to a woman. What conclusion do you think she'll come to?
This game was occasionally subverted by Colin Mochrie, with lines like "No, I don't know what you mean," or "I'm going to go to the bathroom." The other members would simply react in mock disgust when it came to subverting. In contrast to Colin Mochrie, Brad Sherwood was a stand-out in this game.note "Nothing better than a 200 pound snatch, if you know what I mean!" 
As Tom Lehrer put it (heh) in the song Smut, When correctly viewed, everything is lewd!
In an episode of NewsRadio, Bill hastily informs Dave of Lisa's potential sexual endeavors using a euphemism. Dave, who was no longer dating Lisa, doesn't have a strong reaction to the news, which causes Bill and Mr. James to assume he didn't catch the euphemism:
Bill: You know what that means, don't you? Dave: Yes. Mr. James: That means sex. Dave:I know.
In Scrubs, The Todd, who commonly uses the Double Entendre, will also use more obvious references, such as the classic "That's what she said!" or when a character (usually female) mentions they're looking for something, he'll pop up and say "I got your [object sought for] right here!" and motion to his crotch. He'll also explain his references from time to time.
The Todd has even turned the word "innuendo" into a double entendre by saying it as "inYOURendo".
His "I'd like to double her entendre" line.
Michael Scott, of The Office (US), frequently adds "that's what she said" to statements. In the episode Dunder Mifflin Infinity, it was revealed that he keeps a list of things he can say just to be able to add those four words.
Pam: "That job looks hard." "You should put your mouth on that." How can you even use that one naturally?
Michael: Blowing up balloons, I thought.
As noted above, "If you know what I mean, and I think you do." is the catch-phrase of famed drive-in film critic and monster-movie show host Joe Bob Briggs, who wasn't allowed to describe most of the events of the movies he reviewed in his original position as a newspaper film critic.
House provides an inversion when a physical therapist orders Dr. House to use a quad cane:
Cameron: Nice cane.
House: ...if I know what you mean!
House: Dr. Cuddy! LOVE the outfit! Says "I'm professional, but I'm still a woman." Actually, it kinda yells that second part.
Cuddy: Yeah, and your big cane doesn't mean anything either.
And possible one of the crowning examples...
House (handing cane to intern): Here, hold my metaphor for a second.
On Titus, Chris Titus's special brother Dave once had a sequence where he repeatedly made direct references to sex, ending each line with "If you know what I mean!". Like "Sorry we're late me and Nancy were having sex in the car, if you know what I mean", and "That's time you could have spent having sex with Erin if you know what I mean" Chris: "We've all cracked your little code, Dave."
King Zad: Every Terron warrior will have a priceless horn!...so to speak.
On Absolutely Fabulous, Patsy is quite fond of this type of joke—as well as laughing at her own jokes. The best example is probably: "The only thing that got him up in the night was his bladder. D'you get it, Ed? D'you get it? The only thing he got UP for, was to have a slash." (From "Fat")
Chang: "And then she said "screw you!" or "screw education!" or something like that and stormed out of the room in her high-heeled boots like it was tampon time. If you know what I mean." Jeff: "Objection. I don't know what he means." Duncan: "Don't encourage him, Winger."
Dennis/Denise Bryson: More importantly, who is that girl? Dale Cooper: Well now, Denise, I'd have thought you're no longer interested in the opposite sex. Dennis/Denise Bryson: Coop, I may wear women's clothing, but I still put my panties on one leg at a time, if you know what I mean. Dale Cooper: ...not really.
Tara did this in the musical episode of Buffy the Vampire Slayer. It wasn't quite a remark, but the "wink wink, nudge nudge" look she gave Willow when singing "I can feel you inside" erased any possibility that this might have been some kind of metaphor. Her repetition of "You make me com...plete" leading to the song ending with "You make me..." was more than a little suggestive as well.
The entire episode "What Sexual Harris Meant" of Dinosaurs was rife with these - all coming from the character's mouth.
In "The Dogs of War," the second-to-last episode of Star Trek: Deep Space Nine, Zek tells Quark in a comm transmission "I'm retiring. Your mother and I are moving to Risa to enjoy our old age and do a lot of (static), if you know I mean. Quark's response? "Good for you, I guess."
Fist Of Fun's "Four Horsemen waiting for the apocalypse" sketch has Pestilence working as a milkman. One of his customers tells the camera "Although he's a bit odd looking, I know lots of housewives around here would love to get their hands on his extra pinta, if you know what I mean. [Beat] I mean his cock."
Groucho Marx, as host of You Bet Your Life, didn't need to lampshade things that could be construed as double entendres. A quick raise of the eyebrows spoke volumes.
The audience, who got used to this, started lampshading double entendres by laughing even in situations where even Groucho didn't realize something sounded like an innuendo.
"Maybe I can come over later and clean your pipes? Wow, they haven't let me say that in twenty-five years."
In the 'rebrand Margate' task of The Apprentice (UK), Nick Hewer comments on one team's attempts to create photographs of gay couples dancing in a nightclub:
From what I can see, they're not getting a lot of direction, and it's all looking a bit stiff and wooden... if I can put it that way.
In Wizards of Waverly Place, Alex explains to her parents her new idea of a sandwich called "Meet Me In Turkey", then she turns to Justin and grins, telling him that he knows where she's going with that.
In Psych, Shawn says he's selling tickets for the Policemen's Ball. Lassiter says "We don't have balls." Shawn says "There is absolutely nothing I can say to that."
Legendary Bluesman Robert Johnson muttered a sly:"You know what I'm talkin' about" after the line: "You can squeeze my lemon 'til the juice runs down my leg". The line was later appropriated by Led Zeppelin in "The Lemon Song"
Y Ruler of Time: "They're pretty well-developed If You Know What I Mean... And I mean that they're very interesting and rich characters with complex back stories that make them both entertaining and interesting to read about."
Played straight later on when referring to the female leads of "Bleach".
My Cage features a strip were Norm mentions to Rex that even though he wasn't able get a dinner reservation he and Bridget still have "plans" for the night (complete with ribbing and winking)
Rex correctly guesses that said "plans" are eating mac and cheese in front of Heroes
Mrs. Lovett: Think of it as thrift, as a gift, if you get my drift! Todd: No. Mrs. Lovett: Seems an awful waste... I mean, with the price of meat. What it is, when you get it, if you get it... Todd: Ahh... Mrs. Lovett:Good you got it.
The introduction to one translation of Aristophanes' plays gives an example of the difficulties a translator faces: jokes were made about people from the island of Salamis, because they had to row to the mainland, and the ancient Greek word for 'row' had a double meaning. Since modern audiences wouldn't pick up on this, the translators had to add a Lampshaded Double Entendre: "She's from Salamis, need I say more?"
Speaking of "Wink wink nudge nudge say no more" one of the Might and Magic games went just a few steps farther, with a thieves guild saying "wink wink nudge nudge casual looks and glances, need I say more, know what I mean know what I mean?"
Shenmue: "Sailors, Well, I always see them near bars. Well, you know what I mean. I just see them hanging out. Most of them are pretty big, so you can't miss them. Umm, I heard that there's a bar where sailors hang out, but I don't know the place because I never wanted to go to such a bar, you know. It's best to stick to your regular drinking hole, if you know what I mean." I am very afraid that I do know what you mean, Komine.
In Dragon Age: Origins you have option to say "If you know what I mean" while romancing Alistair.
So... have you ever licked a lamppost in winter?
And the Warden's follow up option for both genders: "Why yes, I've licked my fair share of lampposts, and then some." Leaves Alistair gobsmacked.
A side conversation between Alistair and Oghren has them going back and forth about "polishing their weapons." Hilariously, while one of them is saying it in the lampshaded way, the other just means polishing his weapon, with the conversation ending with:
Alistair: Wait, what are you talking about? Oghren: What are you talking about?
In MadWorld, the Black Baron (stop staring) is fond of saying "if you know what I mean" (probably closer to "y'knaw I mean?") after his usually innuendo-laden introductions to the Bloodbath Challenges.
Issun of Ōkami just loves this trope. (Un)fortunately, they go completely over the head of the main target, the busty priestess Rao. (As it turns out, there's a very good reason for that...)
A Kingdom of Loathing item-of-the-month was the naughty origami set, which could be folded and refolded to different items with the message, "You unfold the pieces of paper, if you know what I mean." All of them were sleaze elemental. The riding crop added the 'Innuendo Shopping' effect, which appends "heh heh heh", "if you know what I mean" or "wink wink, nudge nudge" to your chat messages.
Penny Arcade uses this a lot, but in particular exemplified by their recurring newscaster, Randy Pinkwood (whose name in its own right is not so much a Double Entendre as a two single ones).
"I don't know whether she was serious [about Communism], but she certainly seized the means of production, if you know what I'm talking about. And I think you know what I'm talking about. I'm talking about my penis."
Stuff Sucks had this. "I think she wants to be his buddy. (short pause) His sex buddy. (short pause) If you know what I mean."
Outside Interference: The following conversation, after Kate explains to Hollie about her broken arm:
Kate: Sucks, though, 'cause now I have to do everything left-handed.
Hollie: (opens her mouth to speak, grinning broadly)
Played with here in Mountain Time, as it's hard to be sure if we really know what he means. It's not hard to make an educated guess, though.
Webcomics written by members of the United States Air Force, such as Air Force Blues and Crew Dogs, often feature jokes revolving around the frequent real-life use of the catchphrase "so to speak" following any off-color double entendre (intentional or otherwise) by Air Force personnel.
Boy, I'd love to take her out to dinner. And by "take her out to dinner" I mean dunk the donut. And by "dunk the donut" I mean have sex with her. And by "have sex with her" I mean use my penis on her. And by "penis" I mean staple remover. And by "staple" I mean virginity.
Mike Mozart just loves making cracks at toys that look more sexual than they appear.
Red vs. Blue has Tucker and his catchphrase "bow-chika-bow-wow!" He'll say it in response to himself or someone else.
Princess Bubblegum: The dear wanted our sugar, but I didn't give him any.... if you know what I mean. (clicks teeth twice) Finn:(beat) Um...
Then in Puhoy, Finn goes to a Pillow World and dances with a Pillow girl. He comments on how in his world pillows are used for bedding. She giggles, gives a sly grin and states that they are used for that here too. Finn nervously chuckles and blushes.
Animaniacs: Any time a double entendre comes up in the dialog of the show, Yakko would say "Good night everybody!", generally drawing attention to it for those in the know (children probably still didn't get it).
Beavis And Butthead would go into hysterics over any use of the word "wood", "hard", or the like. You can imagine the conversations they had in the movie when they visited the petrified forest.
Clone High's JFK provides us with many such examples, in addition to the page quote.
"Some of us are trying to nail Catharine the Great. Or should I say 'Catharine the SO-SO!'"
"Don't worry, Cleo. I can help you stay up all night long. Notice how I accentuated the words "up" and "long". Now let's bone up for the PXJT test. Guess what the P stands for? PENIS!"
But then, JFK always feels the need to explain the joke flat out, even when completely obvious. His ego simply requires him to brag about his sexual exploits.
Family Guy occasionally features characters wandering completely off subject to point out a double entendre to anyone nearby (such as the fact that the lead character's name is "Peter").
This exchange when Peter and Brian are assembling a crib:
Brian: If you say "that's what she said" again, I'm going to pop you!
Or for that matter....
Quagmire [matter of fact, after a string of Innocent Innuendo comments from Lois]: That one is also sexual.
Spoofed in one episode, where Peter is helping Death get a date. Peter remarks "You might even, you know..." and then proceeds to perform a series of seemingly random, nonsensical motions including breakdance moves. After he finishes, Death says "I don't follow" and Peter (still bent over from one of the dance moves), responds "Intercourse."
Futurama episode "Spanish Fry" has Bender being semi-dedicated to this trope yelling several from off camera, complete with 'WHOOO!', not surprising given that the show is about aliens attempting to harvest Fry's "lower horn" as a potential aphrodisiac.
Fry: Look, normally I'm the first guy to toot his own lower horn...
Bender: I'll say. Whooooo!
Fry: But in this case, I just don't think it's going to work.
Bender: That's what she said. Whooooo!
and later that episode:
Lrrr: Mmm, this jerked chicken is good. I think I'll have Fry's lower horn jerked.
Bender: It's used to it. Whoooo!
Fry: I never thought I'd escape with my doodle but i pulled it out!
Bender: Just like at the movie theater. Whooooo!
The DVD commentary notes that Bender is shouting these comments from offscreen in several cases because they just kept adding more in to lampshade all the entendres.
Black Vulcan's constant habit of appending every double entendre with "In my/his pants."
King of the Hill once featured a (villainous, as far as the show has villains) character who would insert, "That's what she said" in response to anything that could even remotely be considered a Double Entendre.
From another episode:
Coach: Like I tell my gym class, girls can't play sports.
Thatherton: At least I've found one who can get it over the plate, if you know what I mean.
Squirt: It's like they say, "You scratch my belly, I scratch yours." Now excuse me while I take a nap. I've been, uh, scratching a lot of bellies, if you know what I mean. Strudel: Actually, I don't know what he means. Cookie: And I don't wanna know.
Ruth Powers: Well, I know what you're thinking, and the answer is yes. I want to be fixed up with one of your friends as soon as you can arrange it. After all, Homer, I do have the normal... appetites. Homer: Heh, heh, heh... I know what you mean. (pause) Just let me make sure we're not talking about food. Ruth Powers: I'm not. Homer: Right! Me, neither. (pause) We're talking about sex, right? Ruth Powers: Right. Homer: I hear you loud and clear.
"All's Fair In Oven War":
James Caan: Hey Bart, me and Mrs. Krabappel are gonna go play some backgammon, if you know what I mean. Bart: I don't but I hope you win.
In The Venture Bros., Dean is stricken with acute testicular torsion. Billy Quizboy performs surgery on his groin, and when Dean awakens from the anesthesia:
Billy: You're good as new - maybe even better. I hooked you up with "the complete package", if you know what I mean!
Dean: I don't.
American anthropologist Clifford Geertz actually pulled off several academic double entendres in his 1972 book, The Interpretation of Cultures. In chapter 15, which is all about cockfighting in Bali, Geertz makes an obvious double entendre, and lampshades it by saying that the double entendre is entirely intentional in Balinese culture. He then seemingly proceeds to pepper in as many cock-based double entendres as he can. For example, on page 418:
But the intimacy of men with their cocks is more than metaphorical. Balinese men ... spend an enormous amount of time with their favorites, grooming them, feeding them, discussing them ... or just gazing at them with a mixture of rapt admiration and dreamy self-absorption.