The 6 hole - wide 3x3 inside corner bracket is an external fastening method that creates a 90 degree connection. There are three adjacent holes on each side of the bracket. It requires no machining services and can provide infinite positioning along the profile T-slot, allowing a large degree of adjustability. The bracket engages the 2-degree drop-lock feature when the assembly bolts are tightened to the required torque. It is a fastening method that can be repositioned and reused. The suggested mounting hardware can be found on the "Suggested Hardware" tab.