Abstract: A device for stepwise adjustment of the relative positions of two mutually displaceable members (10, 11) comprises a gear rack (13) formed in one (10) of said members, a pin gear (14) with two pin teeth (15) which is mounted for rotation and limited transversal displacement thereof in the other member (11), and means (23) for spring-biasing the pin gear (14) towards a locking position in which the two pin teeth (15) are located in meshing engagement in adjacent tooth gaps of the gear rack (13). Said spring-biasing means (23) are placed in front of the pin teeth (15), on the opposite side thereof with respect to the gear rack (13), and they include a spring-force applying member (23A) which bears resiliently against both pin teeth (15) when the pin gear (14) is in its locking position.