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