Equal spacing trick

I just learned a quick trick used for spacing things out at an equal distance without having to do any complicated math. For example if you want to space out banister for a porch rail. Take a long piece of elastic from a fabric store and use a permanent marker to mark every 2 inches (or another even distance) on the elastic. Now you can stretch the elastic so that two of the marks reach the ends of your length or banister. If you want the banisters spaced farther out then stretch the elastic a little more and eliminate a banister post.