You probably know the basics of how to use a tape measure, but it has a few built-in "features" you may not realise. Case in point: that little slot on the hook can be used to keep the tape measure in place with a nail, or even draw a perfect circle.
This is particularly useful if you're measuring the distance between studs, or nails in a wall for hanging pictures. Just hook the "slot" onto the end of a nail, and measure -- no need to hold it with your hand. You can also hook it onto that nail and use it as an impromptu compass for drawing circles up to 50 feet in radius.
Check out the full video over at the Family Handyman for all the clever things your tape measure can do.
How to Use a Tape Measure [The Family Handyman]