{HEAD ~ The side edges} 2 slope inward from the top of the body board T to {TAIL ~ the bottom surface B} 
slope inward to
{ HEAD ~ The side edges } 2 slope inward from the top of the body board T to { TAIL ~ the bottom surface B }
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL REL OTH OTH OTH OTH OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL