About.com’s page on how to determine if an assembly is square

So, I didn’t use a square when assembling the sides of my ladder bookshelf project.  Is there a way I could have checked for square without breaking out my squares in the first place?

Turns out there’s not just one way – there are TWO easy ways to determine if a project is square using just a lowly tape measure. This site clearly describes the two procedures – the 3-4-5 triangle method, which uses the Pythagorean Theorem to determine if an angle is at 90 degrees.

The other method is very familiar to anyone who has ever watched the New Yankee Workshop.  By measuring the diagonals of a square or rectangular assembly, if the measurements are equal, the assembly is square.

Sure, some of this may seem like common sense.  However, you’d be surprised just how quickly that bit of common sense can be forgotten in the heat of an assembly!