You think all of your measuring devices are the same?
Think again
I use this tool as a calibration control group
Or this T version which helps draw straight lines
Calibration of your tools is a BIG deal especially when dealing with Projects that require a perfect kerf in order to get a perfect fit.
Once you use it you will ask yourself why you did not use it sooner. It will save you a ton of headaches 
Cheers
Sasquatch
I spent a couple of years as an ISO compliance officer at a Switchgear manufacturer. I spent long hours measuring measuring tapes with a standard test gauge and had to throw out approximately 80% of the tapes we would receive in the shop. I know all about the disparity in measurements from so called measuring devices. Funny thing is that the wood shop was used exclusively for crating product, but since they were part of the company, they had to be held to the same strict standards the fab shop was, and our crates were the most dimensionaly accurate in the business…lol
Wow never imagined that the number would be that high. I found about 30-40 % of the measuring devices are off and 100% of those were the low budget ones