Each pair of bracing members defines {HEAD ~ a guide} for {TAIL ~ the displacement} of the end supports of the support roller for the lower belt 
for
Each pair of bracing members defines { HEAD ~ a guide } for { TAIL ~ the displacement } of the end supports of the support roller for the lower belt
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH