Welding Jigs are used to accurately clamp one or more welding pieces in position when forming a weld between one or more welding pieces. It can be partially or fully formed in the welding kit. They are designed by building the first part to the dimensions on the plans and then simply make a jig to fit the first actual part. Another way to design a welding jig is to first cut out all the necessary parts from metal, fit them together, and then build a jig that holds all the parts in place while they are welded.