Actually, it's just an Awl with a built in spool of thread. An Awl is used to punch hole in leather to stitch through. One with a built in spool of thread, gives the advantage of having the thread right at the fingertips, being automatically dispensed as the leather is stitched together. There are different lengths and diameters of needles for different purposes. I have not been able to master the use of this tool as yet. I still mainly stick with pre-punching the holes and saddle-stitching after that. The awl is good for minor repairs and small projects, though.