I use lots of white in my blocks and since I sew at night after work I have trouble determining which side is the RIGHT side espeicially when using tone on tone patterened fabric. So to save time and to avoid "redesigning" the block, I use my fabric pencil and make a small X on the WRONG side of the fabric. Not a pencil pencil but a fabric pencil. I mark the fabric immediately after cutting so I'm all set to go. Markings are on the wrong side...no more guessing, holding fabric to the light, or laying fab on my lap to see which side is up.