Hi, obviously lots of ways to do this, not sure the most elegant, I guess one way is to make a Construction Plane Through Two Edges and choose two of the aluminum extrusion edges that are at the correct side position. This will create a plane with the correct position and orientation for a joint origin. Then just make a sketch (probably good to first activate one of the aluminum extrusion components so the sketch goes in that component) and do Sketch > Project/Include > Project to project the two edges, then draw a line that should snap to the midpoints of those projected lines, and finally create a sketch point that should snap to the midpoint of your drawn line. That point will serve as a location for your rigid joint.
Post if you have any other questions!
Jesse
