138.8mm x138.8mm corner jig with 40mmx40mm holes. Press it flush against any wood, grab onto it with clamps.

Recommended print settings for strength:

• PLA, unless you prefer PC Blend or similarly STIFF filament
• 4 walls
• 0.3mm layer height
• 25% infill
• GRID infill type

Recommended settings are slower than default for STRENGTH. Should produce a 175g print in 4h on P1S, similar for X1C and A1 mini, which is is still faster than default settings for Mk3S by about 50%.

Also on printables: https://www.printables.com/model/642915-chonky-90-degree-corner-jig