Supposedly, the ghosts are appeased by the construction of rooms that precisely re-create the rooms in which they were killed by Winchester rifles. This seemingly is enough to soothe virtually all those who can't rest after dying in this manner, except for the Confederate-soldier-turned-active-shooter who's the main antagonist in the film. But historically, an awful lot of people killed by Winchester rifles in Sarah Winchester's lifetime died outdoors - shot in hunting accidents, cattle wars, skirmishes between Natives and settlers, on battlefields, etc - not in rooms at all.
