Trunking 1, in which the first engagement means comprises a part circular bead formed along {HEAD ~ the free end} of each side wall and of {TAIL ~ radius} greater than the thickness of said side wall 
of
Trunking 1 , in which the first engagement means comprises a part circular bead formed along { HEAD ~ the free end } of each side wall and of { TAIL ~ radius } greater than the thickness of said side wall
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH