Can someone explain to me what it does? I understand "fit to length", just not that one. I wonder if it would stop me from having to adust my size dial over and over to see just how big I can cut something on a 12x12 mat? BTW, I have done waaay more pics for my kid's rooms, just have had nothing but rain and clouds, so no pics yet. Trains and trucks and school busses, oh my.