The 3 hole - inside corner bracket is an external fastening method that creates a 90 degree connection. There are two stacked holes on one side and one hole on the opposite side of the bracket. This fastener requires no machining services and can provide infinite positioning along the profile T-slot, allowing a large degree of adjustability. It is a fastening method that can be repositioned and reused.
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/.
