This small hinge is perfect for little DIY projects. It uses a piece of 1.75mm filament as the pin and is quick and easy to print. Can be mounted with M3 size bolts/screws or double-sided tape.
 

Print instructions:
Layer height: 0.2mm
Infill: 10-25%
Support: Depends on how clean your printer can print overhangs

Assembly instructions:
1. Make sure parts mesh well.
2. With the 2 halfs meshed, insert a piece of filament 35mm long into the hole as the pin.
3. Feel free to use a drop of super glue on the open side to secure the pin in place if it is loose.
4. Mount using an M3 bolt/screw. Double-sided tape works perfectly as well.