{HEAD ~ A retainer} is used for securing {TAIL ~ the skylight cover} over the operating leaf frame 
is used for securing
{ HEAD ~ A retainer } is used for securing { TAIL ~ the skylight cover } over the operating leaf frame
HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH