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