The frame is constructed including a base frame and {TAIL ~ an operating leaf frame} usually referred to as an operating leaf frame or {HEAD ~ operating leaf} 
The frame is constructed including a base frame and { TAIL ~ an operating leaf frame } usually referred to as an operating leaf frame or { HEAD ~ operating leaf }
OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD