The backframe can be switched from {HEAD ~ a fully extended position} under normal use, or {TAIL ~ a collapsible position} under a transportation or storage 
The backframe can be switched from { HEAD ~ a fully extended position } under normal use , or { TAIL ~ a collapsible position } under a transportation or storage
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH