When the actuator is pushed down, {HEAD ~ the downward movement} is controlled by {TAIL ~ the interaction} of the slots with the guide rails 
When the actuator is pushed down , { HEAD ~ the downward movement } is controlled by { TAIL ~ the interaction } of the slots with the guide rails
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH