Tape measure magic.

 After about 50 years of woodworking, and thirty of teaching other woodworkers, it's occurred to me that there are some subtle things that can make things easier and more accurate with a bit of deeper understanding. Often in classes, the simple techniques that I use in setting stop blocks on the sled are not obvious to students. And I often fail to specifically call them out to student attention. Then with students attempting to learn 3 or more things at once, such a simple thing can pass under the radar.