The first edge is pressed against the first rail element through {HEAD ~ a first protruding portion} of {TAIL ~ the first edge} 
The first edge is pressed against the first rail element through { HEAD ~ a first protruding portion } of { TAIL ~ the first edge }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL