Vertex for frame with 20x20 extrusions

I am building a heated chamber for my mendelmax. So I bought aluminium extrusions 20x20. This vertex will fit the extrusions to each other. Be aware, this is for misumi profile (6mm nut). You can change this by editing the provided FreeCAD-Files. There are two versions: With and without my name. You will find the right one :-)
If You are interested in the construction and make of the heated chamber please visit my blog at sturm.selfhost.eu .