The wiring in my apartment is quite old, and I needed a lid for one of the electrical junction boxes. Unfortunately nothing from the hardware store did fit. So … I made my own.

The box  is 90x90mm outer edges.
The holes for swrewing a lid onto it are 84mm apart.
The lid I created covers 110x110mm.

You can scale the model in x- and y-direction to any size, so that it fits your needs.

Made 3 versions

• Lid version 1 - (110x110mm) for an electrical junction box (90x90mm)
  is with clips, which holds itself in place. 
  It has got 4 scales/shingles on each clip to increase friction to the inner wall of the box.
  The inner part of the box should be 79x79mm. Again scale it to your needs.
   
• Lid version 2 (110x110mm) for an electrical junction box (90x90mm)
  has holes exactly 84mm apart, so that I can use screws to fix it to my box.
  I used a cone-drill to make the screws fit better.
  This model is pretty basic. But I share it anyway.
   
• Lid version 3 (125x125mm) for an electrical junction box (60x60mm)
  is also with clips. It is designed to fit into a eletrical box 60x60mm. But it covers 120x120mm. I use it for a smaller electrical junction box, where there are some damages to the wall next to it. So i do not need to apply cement or paint - lazy me ;-)
  Other than that it is the same as version 1

ChangeLog:

• Revision v1 (deleted for versions with clips)
  Clips with a have a depth/strength of 1.2mm. So they turned out to have exactly 2 printlines with my 0.6 nozzle. They broke easly. So I removed this revision.
• Revision v2 (current): 
  Made the clips stronger. Now 1.8mm in depth/strength. So they come out to have 3 printlines with a 0.6 nozzle. They are a bit stiffer now (which is good) and MUCH more durable (which is great).