I've learned the hard way that I really have to square up the units and then blocks as I go along, which really helps once the whole quilt is together. then I measure and if within 1/4" i'm good to go--once I quilt it and trim I will check to make sure not weird, but usually it's in almost perfect square. I will block wallhangings and any quilt for shows, otherwise if it's a bed quilt it won't matter!