This is a NEMA 5-15 dummy socket that I created for another project. NEMA 5-15 is the standard North America 120 volt electrical outlet. 

I designed and iterated for a reasonably snug friction fit but not too tight. Aside perhaps from being useful as a protective cap for your NEMA 5-15 plugs, it doesn't really do anything. I'm sharing it as a template in case someone needs one for a project. There's probably some cool stuff you can think of, like cord storage solutions?

Here's the link to the Tinkercad project if you want to use it. You can ungroup the holes from the cube, then add the holes to your project.

https://www.tinkercad.com/things/fmLX3Lz0Vmx