This is a cutting jig for 2020 aluminum extrusion. I use a jigsaw with a metal blade (a lot easier than swapping out the blade on the chop saw), and I have trouble making true 90 degree cuts. All my normal woodworking jigs are just too large and clunky for this size of stock, so made a small part specifically for this task - works great. Has a flange on the back for easily attaching a clamp. If you do not have steady hands, print two and use one on each side...

In theory this thing could also be used to mount 2020 to a surface...