Abstract: A lateral register system, in particular for flexible printing forms which are held by their edges in an axially extending gap in a plate cylinder, the edges being pre-bent according to the inclination of the gaps. The register system includes an insert strip for each printing form, which insert strip can be inserted into the gap and has at least one stationary register pin. When a plurality of printing forms are to be held in a common gap, the insert strips have different lengths and can be placed one on top of the other so that each printing form can cooperate with the register pin provided for it. Each insert strip can be adjusted individually in the axial direction of the plate cylinder by an adjusting system.