You can easily add a beautiful decorative crochet edging around fabric using the blanket stitch, also called a buttonhole stitch. You've probably seen this done on hankies, but you can do it with any size project (ie: napkins, towels, blankets, etc.) You can also use this stitch to tidy up the edge of a crochet project instead of slip stitching or single crocheting around the project.
How to Make the Blanket Stitch
With the right side of the cloth facing up and the raw edge, or edge to be worked, positioned toward your body, hold the line to be stitched along the cushion of the left forefinger, beginning at the left-hand side of the line.
Begin with several running stitches along the edge to be covered, ending at the point for the purl of the first blanket stitch. The purl of the stitch is where the threads cross creating an edge along the raw edge of the material.
Hold the thread down under your thumb to form a loop. Insert the needle above the line at a point the required depth of the blanket stitch and out at the purl line. Use your running stitches as a guide.
Draw up the loose yarn or thread, lift the thumb, and tighten the purl, but not too firmly as not to pucker the fabric.
Adding Yarn or Thread
If you need to add more yarn or thread, working from the back side of the fabric, with the working thread take two or three running stitches toward the right near the purl line. With the new thread take two or three stitches near the left of the purl line. Bring the needle up the correct side of the fabric between the last two blanket stitches, exactly on the purl line.
Place the needle at the right hand side of the last stitch to complete the purl. Put the needle the wrong side of the fabric and slip the thread or yarn under the completed stitches to hold the end securely.
Once you have the basic blanket stitch down, you can create some interesting modifications by varying the lengths of the stitches and purls.