An actuator engages {HEAD ~ the shaft} for translation from {TAIL ~ a first retracted position} to a second extended position 
An actuator engages { HEAD ~ the shaft } for translation from { TAIL ~ a first retracted position } to a second extended position
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH