I'm fighting with marking out where to put the notches for the ledges. My beams vary some in spacing but they are about 1-1.25" apart. Ledges are supposed to be 9-12" apart so in 1:48 that's .25" to .1875". It crossed my mind that if I had a parallel rule with, say, 5 rules it would make it easy(er) to adjust the spacing when I mark the carlings. Trouble is, the rules would have to be 1/8" or less wide and about 6" long. I don't think I can make something like this. Has anyone ever seen such a thing? Or maybe a better idea for marking these out?