a synchronized palletizer includes a row conveyor and a layer head , each vertically reciprocating within a frame . an infeed conveyor delivers in series items row - by - row onto the row conveyor . the row conveyor moves to vertically coincide with the layer head and laterally transfer a row items onto the layer head . once a complete item layer has been constructed on the layer head , the layer head collapses the layer together and drops the layer through its floor onto a pallet or stack of item layers therebelow . generally , the layer head vertical position follows the top of stack of item layers and the row conveyor travels reciprocally between the infeed conveyor and the layer head to deliver items row - by - row to the layer head . a variety of alternative relative positioning schemes , however , may be implemented .