projection a rectangular frame is clamped by the longitudinal supports 3 and transverse supports 2 one support unit at a time is positioned in each corner of this rectangular frame each support unit is movably fastened both to a longitudinal support 3 and to a transverse support 2 e g in that grooves into which corresponding formations of the support units are fitted extend in the longitudinal direction of the transverse supports 2 and longitudinal supports 3 in this exemplary embodiment each support unit is provided with gluing means 7 in this particular case the gluing means 7 comprises an essentially upwardly directed nozzle and is connected to a storage tank for the glue adhesive etc by means of a hose connection the nozzle is directed at the lower side of a tab of a carton blank to be fitted on in the immediate vicinity of the gluing means 7 a pre folding flap 8 is disposed on each support unit the design of the folding flap 8 will be described further with reference to fig2 each carton blank to be inserted comprises a base 111 see e g fig4 a fixing means 6 located in the corner region of the carton blank 39 s base is disposed on the support unit in each corner.