The longitudinal sides 21, 22 comprise grooves and {HEAD ~ tongues} for joining the longitudinal sides 21, 22 to form the pipeline according to the invention by rolling up {TAIL ~ the portion} of material 19, which longitudinal sides are formed in accordance with the illustration in FIGS 1 and 2 
The longitudinal sides 21 , 22 comprise grooves and { HEAD ~ tongues } for joining the longitudinal sides 21 , 22 to form the pipeline according to the invention by rolling up { TAIL ~ the portion } of material 19 , which longitudinal sides are formed in accordance with the illustration in FIGS 1 and 2
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH