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