Apparatus 1 wherein said {HEAD ~ transverse inverted V shaped fingers} have included {TAIL ~ surfaces} which lie in a pair of intersecting planes W and X, wherein said V shaped groove has included surfaces which lie in a pair of intersecting planes Y and Z, wherein plane W intersects with plane Y in an interior angle γ, wherein plane X intersects with plane Z in an interior angle δ, wherein γ>90°, and wherein δ>90° 
have included
Apparatus 1 wherein said { HEAD ~ transverse inverted V shaped fingers } have included { TAIL ~ surfaces } which lie in a pair of intersecting planes W and X , wherein said V shaped groove has included surfaces which lie in a pair of intersecting planes Y and Z , wherein plane W intersects with plane Y in an interior angle γ , wherein plane X intersects with plane Z in an interior angle δ , wherein γ>90 ° , and wherein δ>90 °
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL 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 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 OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH