I like to square up blocks with the Quilt In a Day Square Up Ruler. It's fast, easy and accurate. All you have to do is put the correct diagonal line for the unfinished size of your block on your diagonal seam, trim a sliver from the side and top if necessary, turn the block 180 degrees and do it again. The blocks are all exactly the correct size and the seams hit the corners exactly. The reason it's fast is that you don't have to keep hunting for the two unfinished size lines on your regular ruler and lining those up with the two edges of your block. Those lines aren't even on the ruler, only the diagonal line is on it. It squares up blocks from 1"-6.5". Love, love, love it.