Flat blanks are fed from a stack by bending back a flap to form an inside corner, engaging the corner with a puller bar and pulling the blank from the stack and along a path past plows which bend the blank to form it about a mandrel while a product to be packaged is moved along inside the mandrel in synchronism with the blank movement. Pusher element retraction means are also disclosed as are rotation means for rotating partially completed cartons to orient extended end tabs and flaps with stationary plows for effecting end closure of the cartons thus formed.