Use this stitch for sewing together moccasins. I use a #6 glover's needle and artificial sinew split in 4.
Thread the needle with about 3 feet of split sinew. Pull the ends of the sinew so that they are even and tie an overhand knot about 1 inch from the bottom, leaving a "tail." Line up the two pieces of leather you're sewing together and insert the threaded needle, from the bottom pushing out through the top, about 1/8 inch from the edge. Pull the needle all the way through but don't pull tight. Now put the needle between the two strands of sinew, just before the knot, creating a loop. Now pull it tight.
Make your next stitch about 1/8 inch from your first stitch, pushing the needle from the bottom up through the top. Pull your stitches tight but do not pucker. The more sinew that gets "buried" in the leather the less there is exposed to wear. Stitch in the "tail" (see above) for the next 3 or 4 stitches. Then trim the remainder of the tail off. Doing this makes the knot less likely to slide off the bottom over time.
Continue whipstitching about 1/8 inch from the edge and about 1/8 inch apart. Try to make your stitches as even as you can as the results will be noticeable in your finished project. When you get to the end of what you are sewing together, insert the needle half-way through the pieces of leather and wrap the sinew 4 times around the exposed needle.
Holding the loops tightly with your other index finger and thumb, use a needlenose pliers to pull the needle through the loops, creating a secure knot.
Take another stitch and repeat by inserting the needle halfways, wrapping the sinew around it 4 times, and pulling the needle through the loops. You will now have two knots close together.
Now push the needle backwards underneath several stitches to "bury" the sinew before trimming it off.