When I make blocks from Quilterscache.com, she always mentions the scant 1/4 seam. I do find, that if I don't move my needle a tad to the right, when I am done with the blocks, they are not 12.5 as many swaps specify. Just moving the needle over a bit ensures my blocks are okay for all the swaps that I do. Over block over block, that scant can add up to making the blocks not square up with each other.