where to stop depends on here the mark is. I believe that a knife scribe is better than a pencil if you have a knife. If you are laying out mortises or tenons the accuracy matters even more. A good marking gauge is essential for making exact duplicate marks when laying out joints. Buy one, no no no
With a little attention to detail and good practices and techniques you can make one as accurate as any you could purchase AND you can customize it to fit your hand or finger grasp. Again some shorts and cutoffs from your keeper bin and some hardware you surely have hanging around. And BOB IS your uncle, bingo a really nice useful tool.
https://literaryworkshop.wordpress.com/ ... ing-gauge/As the article author points out, if you are going to make one, why not a second or even more. One never knows do one when you could use an extra or even a spare part.