We often need to find the centre or midpoint of something, and when it is an odd dimension, dividing by two can be a daunting task.
We went through some rulers and tape measurers that do that automatically, as well as showing how to put a tape measurer on an angle across a board so that it reads an even number. Dividing that by two gives you the middle.
My favorite of all, the centre tape that has regular inches on the top, and half sized inches on the bottom. Find the length of your object on the top, and the same number on the bottom gives you the centre.
The special center rulers came from Lee Valley Tools