{HEAD ~ A seat} includes {TAIL ~ a base} having a block extended rearward for forming a pair of notches 
includes
{ HEAD ~ A seat } includes { TAIL ~ a base } having a block extended rearward for forming a pair of notches
HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH