Carpenter's Square Fence

A fence that can be attached to a carpenter's square, to give it a bigger face to put against an edge that you want to be square to. 

This is similar in concept to commercial fences like the Lee Valley Veritas Square Fence. Those are extruded aluminum, and longer, so probably will be more accurate for heavy duty use. 

I made mine 75 mm long with the intention of using two, to provide a baseline as long as you want. That way it will fit on just about any printer. It easily could be many different lengths, but the accuracy might fade a bit as it gets longer. With two I can verify that the contact faces are coplanar after installation. That doesn't guarantee that it's square, but it should uncover most installation errors. I included 125 mm long version as well. Larger ones could be made.

The screw holes have rooftops, with the intention of printing it vertically. I tried printing it flat, with the slot facing down, but the thin part didn't adhere solidly and kept breaking off during the print. I'm experimenting with printing horizontally with a brim. I included a 125 mm horizontal one as well, but I haven't tried printing that one. The only difference is the location of the flat part of the holes. I updated the 125 horizontal to add some buttresses to improve the stiffness during print. (Version 2)

It is made to use a McMaster-Carr 94615A112 flanged 4-40 insert. The bottom has holes that allow the insert to be passed through and pressed in from the bottom. There is a recess so the flange is recessed below the surface. Right now it just has any old 4-40 screw in it, but I intend to replace those with 98704A105 thumb screws.