Abstract: A spiral slot stacker has a two-part stripper 2 for stripping out sheet material from a stacker wheel 1. The two parts 2a, 2b of the stripper are movable. A first part 2a of the stripper is moved out of the stacker wheel together with the last bank note 100 to be stacked in such a way, that only the last bank note is stripped out and the next bank note 101 remains in the stacker wheel. The second part 2b of the stripper at this stage rotates along with the stacker wheel and will not be locked in the strip-out position until the spiral slot stacker is prepared for stacking a next bank-note stack. The bank notes, in the meanwhile supplied to the stacker wheel, are stripped out from the stacker wheel by the second part 2b of the stripper, while the first part 2a of the stripper is moved back to the strip-out position. By this method a collision of the first part of the stripper with the bank notes located in the stacker wheel is prevented.