Two longitudinally split plastics tubes are fed in parallel by respective feeding means and each have at least one margin folded back to have handle-hole reinforcements applied to it at intervals. The reinforcements are severed from a web by a rotary knife. The handle holes are formed in the tubes by punches simultaneously with the operation of separating welding means for welding off carrier bags from both tubes. Two photocells upstream of the reinforcement applying station scan printed register marks on the tubes and bring the tubes into phase with the rotary knife by operating a respective motor-driven indexing roller for each tube. Two further photocells for scanning the register marks are adapted to stop the feeding means independently when the tubes are correctly positioned in relation to the punches and separating welding means.