A belt assembly which, in operation, can be tensioned along a path, comprising a belt (3, 13, 33) having a toothed surface and a back surface and one unit or a plurality of units (1, 11, 31) fastened to the belt on the side of the back surface. In the area of the or each unit (1, 11, 31), parts (3a, 3b, 13a, 13b, 33a) of the belt (3, 13, 33) are bent out of the path of the belt assembly in the direction of the unit (1, 11, 31). The unit comprises a retention element (9, 19, 39) which is in engagement with the toothed surface (8, 18, 38) of the bent belt parts (3a, 3b, 13a, 13b, 33a).
Further disclosed are units (1, 11, 31) for use in the belt assembly according to the invention.