said {HEAD ~ lead screw} is provided with a key pin for engagement with a recess provided on the screw lock member and for inhibiting said {TAIL ~ lead} screw from rotation when said key pin is engaged with said recess 
said { HEAD ~ lead screw } is provided with a key pin for engagement with a recess provided on the screw lock member and for inhibiting said { TAIL ~ lead } screw from rotation when said key pin is engaged with said recess
OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH