The force of the tumbler spring then pivots the tumbler into its assembled position where {HEAD ~ the detent} is engaged with {TAIL ~ the retaining ledge} 
is engaged with
The force of the tumbler spring then pivots the tumbler into its assembled position where { HEAD ~ the detent } is engaged with { TAIL ~ the retaining ledge }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL