I mentioned this before in another post. People attending a wedding are excited and distracted. If you want them to sign a fabric square for the quilt, I highly recommend having paper templates with the seam allowance (1/4 inch) marked. Have them practice with pencil on the paper template. It helps them judge the spacing of the message. Once they are satisfied with their creation, ask them to write the message on the fabric (which has the seam allowance marked). It is less frustrating for the guests and it makes for a beautiful quilt.