{TAIL ~ a first portion} configured to engage with the inner cam surface of {HEAD ~ the actuator knob} 
{ TAIL ~ a first portion } configured to engage with the inner cam surface of { HEAD ~ the actuator knob }
TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD