The trunking may also include {HEAD ~ a cable retainer} for retaining {TAIL ~ cable} and the like in the channel member 
for retaining
The trunking may also include { HEAD ~ a cable retainer } for retaining { TAIL ~ cable } and the like in the channel member
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH