Abstract: Disclosed is a device for positionally adjusting and releasably locking a chair backrest in any one of a plurality of positions on a seat support member between two extreme positions. The device includes a first bracket adapted to be rigidly secured to the backrest and a second bracket adapted to be rigidly secured to the seat support member and slidably receiving the first bracket for sliding movement between two extreme, longitudinally spaced, first and second positions. A locking mechanism is provided for releasably locking the second bracket to the first bracket, the locking mechanism comprising a longitudinal array of lock stop members on the second bracket confronting a lock element secured to the first bracket, the lock stop members each having a locking surface.

Abstract: Disclosed is a device for positionally adjusting and releasably locking a chair backrest in any of a plurality of positions on a seat support member between two extreme positions. The device includes a first bracket adapted to be rigidly secured to the backrest and a second bracket adapted to be rigidly secured to the seat support member and slidably receiving the first bracket for sliding movement between two extreme, longitudinally spaced, first and second positions. A locking mechanism is provided for releasably locking the second bracket to the first bracket, the locking mechanism comprising a longitudinal array of lock stop members on the second bracket confronting a lock element secured to the first bracket, the lock stop members each having a locking surface.