You posted a comment regarding my post so you will get an answer. I agree using the tab as a ruler is easy but on some engines the marks are hard to get at let alone a straight shot for a good measurement so on those cases I make my paper rulers as described for the degrees I need & turn the slit to the bottom then crawl underneath & make my marks that I need. Since I started doing that & have calipers at my disposal I just do it for any and all markings whether the timing marks are easily accessible or not (works for me)
