I see this term tossed around but don't really understand what the process is. I have an idea of what this means, but can you experts explain the process of making a jig (ex: turbo manifold jig to use to make several other turbo manifolds that are identical)?

 

basically, you make a piece that you can bolt the flanges to and has support for the runners, so you know exactly how to build it, and you keep the flanges exactly where they need to be. it can be tough to picture, but as soon as you see on in person (pictures, anybody?) it all makes sense.

 

If you picture most welded up parts, they don't interlock. Only some manifolds use interlocking tubing (flared on one end), and few materials can withstand the heat from a weld and still hold the parts together.

A basic jig for a turbo exhaust manifold would put the turbo flange just where it would be in the engine bay, and the head flange in the spot it should be relative to the turbo flange. That way you have space to move around it, while still keeping the parts placement all the same.