{TAIL ~ Each stem} is movable between {HEAD ~ a withdrawn position} and an extended position with respect to the base, such that the second end projects from the base when the stem is in the extended position 
{ TAIL ~ Each stem } is movable between { HEAD ~ a withdrawn position } and an extended position with respect to the base , such that the second end projects from the base when the stem is in the extended position
TAIL TAIL TAIL TAIL TAIL TAIL OTH 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 OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH