I needed a way to test trailer wiring without it connected to the tow vehicle.  So this is what i came up with.  Nothing revolutionary, just a box with switches to test trailer circuits using a drill battery.  PLA seems to hold up to the use, but it has started to warp the lid from heat inside my work van.  When i make another one, i am going to use ASA.

Pics are version 1, customized with my logo and a Milwaukee logo.   Files are blank, with some of the shortcomings fixed.  More screw points, sized for M3 heat inserts.  I included a lid with labels and holes, one with just holes and a blank one.  Please do share any ideas for upgrading it.

Designed to hold a Milwaukee M18 battery with this holder by @Wiseone.  https://www.printables.com/model/219711-battery-connector-for-milwaukee-m18-updated-081120

I used these switches:   https://www.amazon.com/dp/B08YWQWF2J?ref=ppx_yo2ov_dt_b_fed_asin_title&th=1

And this voltage gauge:   https://www.amazon.com/dp/B0DB1M5G28?ref=ppx_yo2ov_dt_b_fed_asin_title&th=1

There are prewired 7 way plugs, but I used this one.

https://a.co/d/f21gJx5

Compartment inside hold a old style turn signal flasher.  I will change it to fit a LED flasher when i decide on one.