Abstract: A robotic surgical tool includes a handle providing a plurality of drive inputs, an elongate shaft including a plurality of sliding rack gears movably nested within a corresponding plurality of longitudinal channels defined along the shaft, and an end effector arranged at a distal end of the shaft and an articulable wrist interposing the end effector and the distal end. An actuation system housed in the handle actuates the drive inputs to move the sliding rack gears and thereby causes operation of at least one of the end effector and the wrist. A tailpiece is arranged at a proximal end of the shaft and is operably coupled to the sliding rack gears, the tailpiece includes a housing and a manual actuation device mounted to the housing and manually actuatable to act on the sliding rack gears and thereby operate at least one of the end effector and the wrist.