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