Vertical frame system for a scaffolding system, comprising two vertical posts and a horizontal ledger, which can be detachably connected to one another as intended to form an H-shaped vertical frame, and a locking element (3b, R) for each vertical post, designed to lock the detachable connection, wherein - the horizontal ledger has a bracket at each of its end faces for holding a vertical post, each of the brackets comprising a vertical holding groove and being shaped in such a way that in each case one of the vertical posts can be pushed laterally into the holding groove and is held there form-fit, wherein the brackets are aligned in such a way that the vertical posts can be pushed into the holding grooves from different sides, - each vertical post has in its centre area an at least partially circumferential bulge as a blocking element, which is designed in such a way that it blocks the horizontal ledger from slipping downwards along the vertical post, - each locking element (3b, R) is designed to lock a vertical post in the holding groove, so that in the intended assembled state the horizontal ledger rests on the bulge and the vertical posts are held in the brackets, characterized in that one of the vertical posts has a locking piece which projects laterally from its lateral surface and one of the brackets has an enclosed opening in one of its walls, through which the locking piece can be pushed, and wherein - the locking piece has a hole and is dimensioned and positioned such that, in an intended mounting position of the vertical post in the bracket, the locking piece protrudes through the opening and the vertical post can be locked in the bracket by means of a ledger pushed through the hole, or - the locking piece thickens at its end at a distance from the vertical post and the brackets have an enclosed opening in one of their walls, which opening is shaped in the lower region so that the thickened end of the locking piece can be pushed through and is shaped in the upper region so that the thin region of the locking piece fits through but not the thickened end. - the horizontal ledger has a bracket at each of its end faces for holding a vertical post, each of the brackets comprising a vertical holding groove and being shaped in such a way that in each case one of the vertical posts can be pushed laterally into the holding groove and is held there form-fit, wherein the brackets are aligned in such a way that the vertical posts can be pushed into the holding grooves from different sides, - each vertical post has in its centre area an at least partially circumferential bulge as a blocking element, which is designed in such a way that it blocks the horizontal ledger from slipping downwards along the vertical post, - each locking element (3b, R) is designed to lock a vertical post in the holding groove, so that in the intended assembled state the horizontal ledger rests on the bulge and the vertical posts are held in the brackets, - the locking piece has a hole and is dimensioned and positioned such that, in an intended mounting position of the vertical post in the bracket, the locking piece protrudes through the opening and the vertical post can be locked in the bracket by means of a ledger pushed through the hole, or - the locking piece thickens at its end at a distance from the vertical post and the brackets have an enclosed opening in one of their walls, which opening is shaped in the lower region so that the thickened end of the locking piece can be pushed through and is shaped in the upper region so that the thin region of the locking piece fits through but not the thickened end.