Fastening device for mounting on a mounting rail

A fastening device (21) for mounting on a mounting rail (11) having a rear-engagement member (22) which is configured to be introduced into the mounting opening (15) and to engage behind the rims (14) of the mounting opening (15) of the mounting rail (11); including a tensioning device (32) which cooperates with the rear-engagement member (22) and has a longitudinal axis, for clamping the fastening device (21) to the mounting rail (11); including a contact plate (42) for resting on the outside of the mounting rail (11) that has a feed-through opening for a part of the tensioning device (32); and a spring element (52) configured between the contact plate (42) and the rear-engagement member (22) for preloading the rear-engagement member (22) circumferentially with respect to the longitudinal axis (34) of the tensioning device (32); including a holding device (62) between the rear-engagement member (22) and the contact plate (42) for holding the rear-engagement member (22) in the preloaded position; upon release of the holding device (62), the rear-engagement member (22) being movable by the spring element (52) from the insertion position to a rear-engagement position where it engages behind the rims (14) of the mounting opening (15). One stop element (47) having a stop face for limiting the capacity of the rear-engagement member (22) for twisting rotation is provided on the contact plate (42).