While building robots for First Robotics Competition (FRC), we tend to use a lot of 1" and 1"x2" aluminum tubing and drill lots of holes. Measuring and marking a bunch of 1/4" holes at 1/2" on center, on the center line of a 1" tube takes a long time to do well (using calipers, edge markers) and when students use tape measures, or wooden rulers, the results aren't as precise as needed. While a water-jet or CNC machine would be awesome, this is a little more reasonably priced helper.
Enter the edge-guides. Easy to configure for different size stock, I've added a few of the most commonly used ones.
The 2in edge marker.stl and 4in edge marker.stl have the center line at 1/2" from the edge guide and tic-marks start 1/8" from the side and are at 1/8" intervals.
The 2in cross marker.stl makes tic-marks across a 2" tube, starting at 1/8" from the edge. It's 1/2" wide, with the center line at 1/4" from the end, so it's also good for marking off mounting holes at the end of the stock.
Added a 3/4" wide guide for some flat stock we're using. Also, the gcode for all four of these to be printed together. These settings worked well for me with PLA.
Update 3/1/2016 : Modified scad for a multi_edge_guide which allows for passing the locations for one or more of the sets of tic marks, vs the original which just allowed one mid way through the width. This lets me make a single guide for 2" tubing with 2 sets of marks, one at 0.5" and the other at 1.5" from the edge guide so both sets are based on the same reference edge. Also added the .stl for that guide.
Did all these in PLA with 0.1mm layer height. Probably could have slowed the print down a little bit for more precision, but they've worked fine at Cura's easy settings "normal" print speeds.