A mechanism for moving two alignment devices having vertical parallel faces for identical flat workpieces such as cardboard blanks, simultaneously in opposite directions. The mechanism includes two reciprocating slides that simultaneously drive the alignment devices in opposite directions. The slides are operated by an articulated mechanism including a pair of extension arms and a drive cradle attached to an oscillating shaft. Actuate projections on the drive cradle engage rotationally with complementary arcuate surfaces on coupling mechanisms, preferably formed of a plastic material such as PETP, attached to the extension arms as the shaft oscillates. Compression springs bias the extension arms and the associated coupling mechanisms against the projections to eliminate the effect of wear in the mechanism.