Abstract: Apparatus for successively indexing slots of a wafer carrier into position at an end of a conveying means, such as an air slide, utilizes motion of a rotary drive means to move pins within drive slots and impart motion to the carrier. As the rotary drive head rotates, a pin moves down into a drive slot, pushes against a sidewall of the slot to move the carrier, then retracts back to the end of the slot. With proper positioning of the rotary drive means, the pins also serve to prevent extraneous motion of the carrier when the drive means is not rotating. This apparatus has negligible starting torque when rotation of the drive means begins, and has smooth acceleration and deceleration of the carrier as its motion stops and starts.