SimFlex Expanding Sewing Gauge for Shirring, Smocking, Button, Eyes, Drapery Pleats, Dress Pleats & Much More
I use this tool ALL THE TIME. First off, it's pretty fun to use (I love a good gadget), and secondly, if you're altering the length of a garment you need to change those button holes anyways! I love using it to get the perfect placement when I have a limited number of buttons, or when I have a stash of them and I want to squeeze on just one more... (If you are a vintage button hoarder like me, you know EXACTLY what I mean).
It is quick and easy to use. Simply lay it over your garment and expand it to the desired length for perfectly measured equal distances and accurate spacing from 3/8" to 3 3/8". Expands to a total of 24".