The block 14 wherein said block protrusion comprises first and second oblong sections between which is positioned a joining section, said joining {HEAD ~ section} having {TAIL ~ a narrower width} than either of said first and second oblong sections 
The block 14 wherein said block protrusion comprises first and second oblong sections between which is positioned a joining section , said joining { HEAD ~ section } having { TAIL ~ a narrower width } than either of said first and second oblong sections
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH