{HEAD ~ The backframe} is configured by {TAIL ~ interlinked linkages} such that the backframe can be locked in a fully extended position in use, or be collapsible when not in use in a way that the overall dimension of the collapsible backframe is smaller than the fully extended backframe 
is configured by
{ HEAD ~ The backframe } is configured by { TAIL ~ interlinked linkages } such that the backframe can be locked in a fully extended position in use , or be collapsible when not in use in a way that the overall dimension of the collapsible backframe is smaller than the fully extended backframe
HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH