The 2 hole - inside corner bracket with single support is an external fastening method that creates a 90 degree connection. The single support provides additional strength while the slotted mounting holes allow for greater adjustability between the connecting profiles. This bracket requires no machining services and can provide infinite positioning along the profile T-slot. The suggested mounting hardware can be found on the "Suggested Hardware" tab.
For technical details and images, please search for the product using the 80/20 interactive catalogue found here: https://catalogs.8020.net/80-20-Catalog-26/C/.