Read more about what this part is for its full description here: https://reactorforge.com/power-progress/
This assembly houses 3 Burndy splicers (PN: AMS2BAG2R). It does a few important things, it isolates them from each other, from the breaker box, and it snaps closed to prevent the lugs from sliding out (and attacking passer buys). On the side where the wires enter the assembly from the breaker, it is closed off except for holes just big enough for them, so it’s impossible for the splicers to slide out from that side. There are also ears on the front to keep the entire assembly from sliding all the way in the breaker box.
The orange printed part in the photos above is an early prototype in PLA. The final version is printed in natural Bridge taulman3D industrial high strength nylon. It is insanely strong!
Be careful when removing the support between the slide body and it's tabs. If you printed them in the original orientation they should be strong enough to handle a good bit of bending them around though.
Be sure to consider the print angle on the slide lock. Grain direction matters for strength in the proper direction, although I saw little difference using nylon with good layer adhesion at horizontal, vertical, and 60-degree print orientations.