Abstract: An improved, tamper-resistant lock and key assembly is provided of the type which includes a key having a post and a generally cup-shaped bit having a bitting formed on the outer end thereof, a generally hollow cylinder, and a circular, pin-type tumbler mechanism housed within the cylinder and defining therewith an annular keyway. The key may be inserted a fixed distance into the keyway to permit rotation thereof between a release and locking position. The improved assembly provides a key having a key bit which has a notched portion formed therein radially inwardly of the bitting thereof and means for obstructing direct access of the key bit to the keyway. The obstruction means includes an obstruction member spaced above and generally overlying the keyway, which necessitates lateral shifting of the key bit therebelow to effect alignment thereof with the keyway.

Abstract: A lock mechanism having a casing through which a spring-biased bolt is slidably movable, the bolt having an end which can be normally extended for a relatively short distance beyond the casing to assume a so-called "latching" position. A slidable sensing bar is arranged alongside of the bolt and in sliding contact therewith and the sensing bar is spring-biased so that it normally projects out of the casing for a distance co-extensive with the bolt while the bolt is either retracted or is in its latching position. A roller carried by the bolt is interposed between the bolt and the sensing bar and is confined in the casing in such a manner that while it rests upon a cam portion of the sensing bar, its bodily movement in the casing will be limited by a stop located therein and the bolt and the sensing bar will be maintained together in either the fully retracted position of the bolt or in its latching position.