Also, along with the other comments about rulers and cutting, I have to say that when I started using a different, thinner bobbin thread, my own blocks were much more accurate. Why? Because you can press the seams flatter with a thinner thread. I use either The Bottom Line by Superior Threads or Guttermann bobbin thread. Guttermann is available at Jo-Ann's. The slight extra cost is more than worth it when I am not encountering hours of frustration when blocks or their sub-units are too small.