From DT Online
A Jig is a specially made piece of equipment used to guide another tool .
- A drilling jig for example can be used accurately to position holes as they are drilled into a work-piece (a Dowel Jig).
- A Dovetail Jig is used to guide a Router Cutter to enable a line of joints accurately to be cut.
- A sawing jig may be used to guide a saw or to enable pieces of material to be sawn to a standard length without the need for repeated marking out.