20 Sets Black 2020 Series Aluminum Extrusion Corner Bracket Kit, Includes 20pcs Right Angle Connectors, 40pcs M5 T Slot Nuts and Screws for 20 Series V-Slot Aluminum Profile Accessories

I'm getting ready to move, and I bought some of these corner brackets. I used 4 of them to lock the gantry in the Y position, two one either side, so it cannot move, and then 2 more, 1 on either side of the print head so it cannot move in the X direction. You can also print some larger corner braces to secure the frame.