A better quality framing square is in order, but the drafting triangles were handy and have nice sharp square edges.
Also, I wanted an easy way of checking for parallelism and equal distance between towers. Theoretically, if all towers are square, the other values should fall in line, AND I always like to double check using a different method.
The pictures below are the end result using drafting triangles aided by a piece of tap or a thin marker.
If you tuck the triangles into the slots, you can bias them tightly to the insides of the extrusion channel. They are also thin enough that they don't bind in the extrusion when you rotate them together.
The spring clamp was there to aid in taking pictures, but ideally, you should not use it and use hand pressure only.
1. You can check for square at the base by holding each triangle firmly to the tower extrusions and slide then down to the print surface or top plate.
2. If the bottom of the triangles are parallel with each other, you now know the towers are parallel to each other.
3. If you mark the triangle overlap with a pieces of tape or marker and move them up and down or between pairs of towers, you can visually check for equal distance assuming you meet the #2 requirement.
4. At any point along the length of the extrusions, 2 and 3 should be good, otherwise that could be an indicator of a bent tower.
Those familiar with winding sticks should feel very comfortable with sighting for parallelism.
