Originally Posted by jitkaau

I believe you can use any rule or mat to measure, so long as you remain consistent. By that I mean that you use the same measuring instrument throughout the project and don't interchange between the mat and the rule or use any other rules in the process as there will be small inconsistencies in all of them and each minute "wrong" measurement will be multiplied by the number of units you are making and therefore will become a big mistake later.