The 4 hole - concealed hinge allows you to design doors with hidden hinges when the door is closed. The hinge mounts to the inside of the frame, which makes enclosures more secure; they are not able to be dismantled when the door is shut.
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/.