Well, pardon me. I think it was a grease pencil then, not wax pencil. Funny thing is, when I Googled grease pencil to see what it is , a picture from Ali Baba was shown for grease pencils and it said all the words in this thread (wax, grease, crayon) !!!! Maybe they are the same. I don't know. But I know they are close to each other more than a Sharpie or chalk.

BTW, I am stocking on chalk also. Bought 5 boxes. They will be needed when I build my new home (concrete and blocks here , not wood) and I have the experience that when you need something like a switch or power outlet exactly placed, then better make a mark on the wall to guarantee no mistakes. BTDT