As can be seen in FIG 3, alignment hole 16 is in {TAIL ~ the shape} of {HEAD ~ a comer} cut out 
As can be seen in FIG 3 , alignment hole 16 is in { TAIL ~ the shape } of { HEAD ~ a comer } cut out
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH