This is the old design. Updated V2 design can be found at:
https://www.prusaprinters.org/prints/32658-lack-enclosure-leg-bracket-v2

I designed this bracket in Fusion 360 to address a wobbling issue I was having with my Lack Enclosure V2. They are an extreme overkill solution, but they're light weight and I think they look nice.

I designed them to have a high stiffness to weight ratio. It was originally designed to be printed in PLA due to its inherent stiffness, but I've found even PETG comes out surprisingly stiff with this material arrangement.

It's still a work in progress. I want to move the screw holes out from the main structure a bit for ease of access to the screws and chamfer a few edges to allow better printability without supports. I also want to add another set of screw holes to the 90 degree corner to allow for more versatility with the design and open it up to be used for other things (shelves and such).

The screw holes are 3.8 mm as this was the best fit for the screws I had on hand.

Print instructions

I recommend printing with the shortest leg of the triangle on the print bed. Be aware it's a tall print (200mm tall) in this orientation. Also recommend 4 perimeters for stiffness. Infill doesn't really matter. It's only in the corners where it's rounded and don't add much to the structure.

Supports may not be strictly necessary on some printers, but it comes out significantly cleaner if you enforce supports under the bottom of the center triangular hole (Pictured above with supports still intact for reference and included the .3mf file with support enforcer already in place). I'm working on a newer version with a chamferred edge in that spot to reduce this need.