You've probably taken the needle back through the same hole it came through and pulled the knot with it. Avoid the holes in the aidaThe most common fabric used for cross stitch, and the best one to use for your first project. It is woven into blocks marked out by regularly-spaced holes. Use these holes to work your cross stitches. Aida is sold in various sizes or counts. The most popular size is 14-count. and push the needle back down one or two threads to the side.