Woodworking Jigs & Fixtures
Woodworking jigs help you make straight cuts, centered holes and that woodworking pieces are square. Jigs help you be more efficient, accurate, and protected too. They are like an extra set of really sturdy hands to help you out.
Many jigs are worth the time it takes to make them because you'll be using them over and over again for many years. (You just have to remember where you stored them!)
Woodworking Jig Parts
Many jigs can be made with scrap wood from older projects. However, larger jigs will probable require you get some fixture components for the construction. A very good material to have on hand for making jigs is MDF, in various thicknesses. MDF is great for jig because it is already flat, easy to machine, and holds screws well.
Which comes to the only other thing you will usually need are screws, again of varying lengths. Often though, when you don't want to permanently attach pieces together, small bar clamps, or C-clamps will be used.
Jig or Fixture
Most woodworkers just call them jigs, but technically there is a difference between the two. A jig will restrict the tool to cutting in a certain place. A fixture holds the work piece (at a desired angle, for example) to make the cut. Honestly, it doesn't really make a difference as long as you build it to make the cut properly and safely.