Of all the 9 boxes we released lately, this one belongs to the smallest ones, as well as HF-N-23 and HF-N-5. HF-N-48 has a special design.
It has three square holes, one on one side and two on the other side, and two round holes, each side by one. You can hold your circuit in the case and lead the connecting lines out through those square holes.
As to the round holes, they are prepared for the situation that you need to fix the case on some other surface. It’s convenient to screw it tightly through those round holes. Here are some details about this one: