What's wrong with finger and thumb?
At Nav School, on one early exercise, the instructor 'confiscates' all the nav kit except for chart, pencil and chinagraph.
No straight edge, protractor or whiz wheel. The stude may improvise to draw straight lines but has to estimate distances and judge angles. They had about 10 minutes to prepare an RTB of about 200 miles.
Oddly not one stude ever thought to take a section of map and use it as a straight edge and measuring tool.