A layer of {HEAD ~ a resilient and crush resistant polymer} is interposed horizontally at any level through the entire thickness of the material of {TAIL ~ said elements} 
A layer of { HEAD ~ a resilient and crush resistant polymer } is interposed horizontally at any level through the entire thickness of the material of { TAIL ~ said elements }
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL