Is That A Ruler In Your Pocket?

Here's a neat post on how to use an ordinary piece of notebook paper (8.5" x 11") as a 12-inch ruler:

Take the first page, and fold from either top corner down to the side, lining up the side carefully, making a right triangle.

Remember how you thought you'd never use trig? Well you were right, because I just used it for you. One ABC and three squares later, the hypotenuse of the right triangle you've created is 12.02 inches - very close to being exactly one foot.

Of course, dollar bills work great too!

Hattip to LifeHacker for linking to this.