Jigs (Vorrichtungen, Werkstatthilfen) are helpers for difficult standard operations, such as drilling angled holes, making specific cuts, or accurately repeating something.
They can usually be self-made! Please share your jigs if they can benefit others - it's as easy as labeling them with a meaningful name and creating a corresponding wiki page with instructions! Every page in the "Jigs" category shows up on the bottom of this page for everyone to find.
Good to know for adjustable jigs: M6 screws advance exactly 1 mm per turn.
Here are some ideas for commonly needed jigs if you feel inclined to make one: