Another remix of a remix of a remix. Really loved the idea but wanted to include a small ruler on the tool so that I could level out the tool and then mark different distances. Also added some minor beveling to the sight pictures of target to improve visibility. Removed the bottom sight picture as I found dust was falling into it and wedging between the tool and the wall. I've included multiple STLs with various options on where ruler markings are.

Ruler is in MM only. Marks are through 0.5mm extrusions on surface. with marks every 0.8mm and each being 0.2mm wide. This allows you to mark from the middle of each extrusion and improve your accuracy. I put this next to another ruler I had and it seems to line up quite well. More accurate than I am anyways.

The markings themselves are every 1mm with large markings every 5mm. No differentiation for each 10mm. I looked at extruding numbers but it looked messy.

Showing my print results here, gets a little ugly where I have some lines overlapping but I consider it totally usable. I wanted to have markings on the top, sides as well as the guide sights on the sides. This lets me know at a glance how far away I might be from another mark.