{HEAD ~ Alignment hole} 17 is also in the shape of {TAIL ~ a comer} cut out 
{ HEAD ~ Alignment hole } 17 is also in the shape of { TAIL ~ a comer } cut out
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH