The shim is then formed to include {HEAD ~ a feature} on its surface which complements the surface profile of {TAIL ~ the assembly surface} 
The shim is then formed to include { HEAD ~ a feature } on its surface which complements the surface profile of { TAIL ~ the assembly surface }
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL