Al Stohlman does a good job of showing this in his book on hand stitching leather. The illustrations say a lot. Basically, you put a needle on each end of the thread. Start with 5 times the distance to sew on a couble layer of holster leather. Stick one needle through the third hole from the end and backstitch to the beginning, running both needles through and pulling each stitch tight. Then do the same all the way down the piece. At the end, backstitch again for two or three holes and pull the thread tight with a single knot that will get buried in the last hole. You can then cut the thread on both sides or cut the back side and pull the other one through the next hole before cutting it.