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