first time post here guys all your help and advice needed Got 2 new cills for the aboveones on the car completely rotten also some of the inner cills and outer edges of floor pan what do i need to do Very new to this so make it as simple as u can cheers guys
I've never really messed around with Renault 5s, but sills are sills. Here's my 10 point guide:
Get the door gaps right before starting and brace them by welding bars across. Otherwise they'll pull together when you fit the new sills.
Strip the old panels off (angle grinder does the job).
Prepare everything for welding (weld new bits in where you have ragged edges). Get everything you want to weld to shiny. Prepare the edge of the floor too but don't weld the panel in yet.
Position the inner sill and tack it in place (just a couple of tacks). Trial fit the outer sill and the door and if it's not right remove the inner sill and reposition it and test the alignment again.
Lots more tacks on the inner sill then seam or plug weld it in place.
I have a Renault 5 Mk1 that looks like it's made of Baguette crusts. Far too rusty to save but the engine will come in handy.
For a 3 door car it's normally OK to brace across the door gap. There is normally plenty of structure behind the door that would act as a brace to keep the car in shape.