Tech ? For arc welding you get yourself a length of cable and...

Tech ? For arc welding you get yourself a length of cable and crimp a lug at one end and a screw a connector to the other end and you have yourself a welding cable ready to screw to the welding machine and connect a handpiece to it.
On SAW welders its lugs at both ends and you may need 2,3,4 or more 700A cables in parallel to get enough amps from the power supply.
30 odd years ago when diesel welders on sites were putting out only 300A max we'd connect 3 of them using 3x 500A cables to an automated SAW inside a cage running on top of a tank and the thing would be welding for hours non stop with T/As inside the tank pulling and untangling the cables from time to time. Definitely heavy but nowhere near as big as your thigh or else they would have needed cranes each time they moved 3x 20-30mtrs of cables. Of course these days you need a licenced sparky to fit a lug or a connector to AS and rules but back then it was the trade assistant's job or the storeman would make welding cables in his spare time. If they stuffed up "the tech behind it" the cable connectors would arc or get hot and they had to redo it again.