{TAIL ~ The arms} 13,14 maintain {HEAD ~ their inward positions}, as shown in FIG 2b, during the movement thereby preventing stacks falling during the motion 
{ TAIL ~ The arms } 13,14 maintain { HEAD ~ their inward positions } , as shown in FIG 2b , during the movement thereby preventing stacks falling during the motion
TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH