When the edges to be whipstitched are either the top or bottom of the pieces, use this method:
1. Hold the pieces so that the stitches from each piece line up together.
2. Using a yarn needle thread with yarn in a matching color (contrasting color used in photo for demonstration purposes), insert the needle from front to back through the first stitch of both pieces.
3. Loosely tie a knot to hold the yarn in place.
4. Insert the needle from front to back into the next stitch of both pieces.
5. First whipstitch is complete.
6. Continue in this way, inserting the needle from front to back through each stitch across to the end.
7. Once the seam is complete, cut the yarn and thread it back through the seam to hide the end.
8. Whipstitch is complete.
When the edges to be whipstitched are the sides of the pieces, the technique is the same except the rows are lined up and the needle is inserted in the ends of rows instead of individual stitches: