jackscrew

n. a threaded rod used for centering and balancing a vault door & frame in position during installation

jamb

n. the vertical components of a door frame

jiggered finish

n. a surface adorned with overlapping concentric circles

jimmy proof

adj. pertaining to a lock having a bolt which interlocks with its strike

JIS

abb. Japanese Industrial Standard

jumbo cylinder

n. a rim or mortise cylinder of 1-1/2" diameter

Source: Lock Industry Standards and Training (LIST) Council