Basic Trope: A promotional matchbook serves as a clue to a suspect's movements.
Straight: P.I. Dirk Bullett rifled through the pockets of the rapidly cooling stiff. What's this? A matchbook from Lucy's Cathouse. Now there's a name he thought he'd never see again. An old flame - but a new lead...
Exaggerated: Bullett was surprised, despite himself. He never woulda thought that matchbook in his pocket would be enough evidence to convict the guy in court...
Downplayed: By itself, he'd have dismissed the matchbook - anyone could pick one of those up. But with a receipt for three hours' worth of drinks, it looked like this guy had taken his time at Lucy's.
Justified: The matchbook didn't prove anything, sure... but it had opened the door to a whole new avenue of investigation. Dirk was back in the game.
Inverted: "I see there's a matchbook missing from the display there, Luce. The guy I'm after, he smokes like a factory chimney, and I know he stopped by here. If you can remember the guy took that 'book, you might blow this case wide open for me..."
Subverted: Dirk cursed. No-one at Lucy's had seen the guy, so it looked like he'd spent two days chasing a wild goose and all he'd caught was a red herring.
Double Subverted: ...but just as he turned the corner, a notebook hit the pavement in front of him. Looking up, he saw an upstairs window slam and a hooker duck out of view. Fishing the note offa the rain-slick pavement, he read, "Someone's been blowing smoke. Meet me midnight tonight, Le Cafe Noir. A friend."
Parodied: Dirk had first thought, when he found 16 matchbooks on one guy, all from different dives, that the guy was a heavy smooker with a taste for call-girls. What a dunce, he thought, as he slugged down another bourbon. Who'd'a thought the stiff was a matchbook salesman?
Zig Zagged: Dirk had found a matchbook on the stiff, but it seems nobody there knew the poor schmo. Just as Dirk was about to leave, a man called out, saying that another patron of the bar was friends with the guy. Dirk couldn't find the friend all day, but as soon as he went back to the bar for a stiff drink, he saw the man sitting at the bar.
Averted: "Damn," Dirk growled. He'd searched the stiff's pockets and just found a whole lotta nothing. It looked like he'd have to try looking for clues somewhere else.
Enforced: Dirk's unflappable facade cracked a faint smile. He'd known he was in a Film Noirparody the moment the dame with the cigarette holder stepped through his office door. He'd been counting the seconds til he'd find a significant matchbook.
Lampshaded: "Oh look, Slim. You got a matchbook. What's the odds this insignificant detail is going to break the case open for me?"
Invoked: A smart bunch, Dirk mused. They'd put a false matchbook on their guy just in case he bought the farm, and it'd led the P.I. straight into an ambush.
Exploited: Dirk grinned, pulling out one of his own matchbooks from the place near his house. Placing it on the body he drove over there, waiting for somebody to go around there, asking about their "friend".
Defied: Dirk had chased too many matchbooks as a rookie, and they never led anywhere. So the guy was at a bar sometime, what's that gonna prove?
Discussed: "Let's see what's in those pockets, Slim. A dime to a dollar says you got a matchbook in there'll tell me where you been hidin' out."
Conversed: Dirk rolled his eyes. If only it was as easy as it was in the pulps - mobsters never came with handy matchbooks in real life.