A retainer extends about the periphery of the skylight for holding {HEAD ~ the panels} on {TAIL ~ the frame} means 
on
A retainer extends about the periphery of the skylight for holding { HEAD ~ the panels } on { TAIL ~ the frame } means
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH