In {HEAD ~ accordance} with another feature of the present invention, the abutting edges may also have toothed portions defined by straight lines, for example, toothed portions formed by {TAIL ~ triangles}, rectangles or trapezoids 
In { HEAD ~ accordance } with another feature of the present invention , the abutting edges may also have toothed portions defined by straight lines , for example , toothed portions formed by { TAIL ~ triangles } , rectangles or trapezoids
OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH