Terminal Box (3D Printing)
I wanted to connect a TV  and 4G router to my boat 12V electrical supply. The boat already had a TV aerial amplifier connected to the AUX circuit but it was at the back of a small cupboard and that not easy to access. I found some useful terminal blocks that included multiway fork connections that looked ideal:-
However, although these have covers, they're pretty basic and I wanted to enclose them in a box.

I drafted up this simple design incorporating recessed segments for the terminals and holes for the nuts and bolts:-

Here are the printed parts with the terminals fitted:-

I mounted the box using Velcro so that it could easily be lifted out with suitably long wire to allow easier access:-

I connected the TV power cable and lengthened TV aerial connection directly to this box and also connected an extension through into the cabin area with a simple uncovered base version :-

This one is located well away from any other wires, so I didn't need any additional cover. To this I connected my 4G router and also a new Amazon Echo Dot; these are 12V unlike the earlier 5V ones, so ideal for connection into the boat electrics. I was able to locate this above a rear trim panel within easy reach and has two spare terminals for connection of any future peripherals.

The whole setup: TV, aerial amplifier, 4G router, and Echo Dot can now just be switched on by the boat control panel AUX switch.

To lessen the overall load on the batteries, I also took the opportunity to change out all the cabin 10W halogen light bulbs for 1.2W LEDs