Abstract: The instrument is a slide caliper with inner and outer feelers borne by a slideblock (3) and by a slider (6) which is mounted for sliding on the slideblock via a play take-up device (7).That device comprises a base plate (10) having two symmetric end inclined planes (14) on which two shoes (11) are arranged. The base plate bears a central shoulder (16) pierced by a hole (17) in which there is engaged the stud (25) of a drive and locking screw. Two compression springs (12) are interposed between this shoulder and the two shoes in order to cause the latter to rise on the inclined planes.This device automatically takes up the play formed by the sliding system. It is irreversible.The shoes (11) are narrower than the base plate and means (22) are provided to avoid their rubbing against the walls of the slider.