The invention proposes a lock for a door or a tailgate on a motor vehicle, having a plastics-material lock housing (2) which is arranged on the door or tailgate, is designed as a guide track (6) for a locking strap (5) or locking bolts and, at the introduction end of the said guide track (6), has at least one spring lip (8) which extends longitudinally into the guide track (6), is formed in one piece with the lock housing (2) and is intended for resiliently supporting the locking strap (5) or locking bolt in the locked position of the lock, and during introduction of the locking strap (5) or locking bolt into the guide track (6), or removal therefrom, and also has a rotary latch (3), wherein the at least one spring lip (8), at least in the region of its free end, which corresponds to the end position and supporting position (9) of the locking strap (5); or locking bolt in the locked position of the lock, has a rest (10) with a low-friction and wear-resistant surface.