the cylinder and a rear edge of the flexible printing form being fixable by at least one resilient retaining element mountable actuatably on the crosspiece and having a hook shaped projection at an end thereof directed towards the circumferential surface of the printing form includes a plurality of the retaining elements mountable alongside one another and stop elements for form lockingly locking the retaining elements on the crosspiece application_number US 64363796 A description referring now to the drawings and first particularly to fig1 thereof there is shown therein a crosspiece 6 which in this embodiment of the invention is formed for example of a round bar and is housed in a gap 5 formed in the printing form cylinder 1 another gap 2 opening out at the circumferential surface of the cylinder 1 is delimited on the one hand by a corner 4 and on the other hand by a side 3 a front edge 8 of a printing form 7 bears against the corner 4 and the rear edge 9 of the printing form 7 is fixed to a retaining element 10 which abuts against the rear side 3 of the gap 2 the printing form 7 is thus stretched or tautened on the circumference of the cylinder 1 the retaining element 10 illustrated in fig1 is formed with a projection 11 in the shape of a hook.