Abstract: A counter for a stack of sheets has a fixed elongate member (21) defining a curved surface (22) in which is formed a vacuum port (23), and a pin (17) extending parallel to the member (21) and arranged to move in a circular orbit therearound. A valve member (25A) is rotatable within the member (21) in synchronism with the motion of the pin (17), and has a port (45) which comes into and out of register with port (23). the corner regions of successive sheets in a stack are drawn in turn on to the curved surface (22) by suction when ports (23) and (45) are in register, so separating the drawn corner from the stack; the pin (17) enters the gap thus created, and transfers that sheet corner to the other side of member (21). The ports (23) and (45) are out of register during this transfer, whereby the corner of the sheet being transferred is no longer held to the member (21 ).