The design of case control studies, looking at past events, generally prevents definitive conclusions.

Such design originally prevented candidates from guessing an answer they did not know, but that would also be very dangerous in some confusing questions.

Improved safety: The design prevents a round from moving within or falling out of the barrel, even if the muzzle looks down.

The design of many playgrounds prevented her students from playing on them.

The double blind design can prevent the experiment from the observer-expectancy effects.

This design prevents the possible entanglement of vegetation among the flutes.

This design prevented papers from falling out of the Trapper's pockets when it was closed.

The system's design also prevents the failure of a single component from "cascading" through other components.

Yet its unspectacular design did not prevent it from being by far the most spectacular thing Ginger had ever seen.

This design also prevented the outsiders from boarding the ship and aiming at the personnel inside.