A slightly wrong alignment will allow opening. Various design techniques have all but eliminated the ability to use sound, feel, tumbler balance, and radiology to defeat combination locks. The bolt assembly consists of a bolt, a rollback and a refractor which translates the rotating motion of the cylinder plug through the action of a tail piece or cam, connected to the bolt assembly, into the linear motion of the bolt. Cylinder locks using pin tumblers are the usual mechanisms used on standard residential and light commercial doors which will be covered here. Very little security due to low throw and shape.
Plastic cards can slide against bevel face.
Anti-shim device added but easily defeated by snapping with screw driver. See P134 Fig 6-17 for variations. For thin doors a pivoting or horizontal deadbolt is used, see 17a. 135 Fig 6-18a. Most common in the past.