You need to print two pairs to join two rails. No supports required.
The following additional hardware is required:
The top plate is press fit into the bottom plate, you can shave a little to push in place by hand.
Dimensions are a copy of the original makita connections adjusted for 3d printing.
I can't recommend using these since they are not as stiff as the original, metal, plates, if you are going to use them try to have the makita/festool connections underneath and use these only at the top of the rail.
I have 3 rails and only one connector but I need a way to join the three rails while I get another link.
The author marked this model as their own original creation.