Machine Stitch Vs. Hand Stitch
Sewing Machine Lock Stitch
A sewing machine uses essentially one type of stitch regardless of the pattern it produces. This stitch is called a lock stitch. A lock stitch utilizes two threads, one on the topside of the fabric and one on the underside of the fabric. These two threads are then crossed in the hole that the needle creates while sewing. While the stitch is strong, it is completely dependent on one thread to hold the other thread in place. If one string breaks or is cut then the entire stitch unravels. Have you ever had a stray thread dangle from your favorite t-shirt and in an attempt to be-rid the nuisance thread you grab it and give it a yank and the entire hem on your shirt comes undone? Yeah! "What the heck" and some other unmentionable words come out of your mouth. I know. This was caused by that lock stitch being unraveled and no longer holding that stitch in place.
Hand Sewn Saddle Stitch
The Saddle Stitch has been around since medieval times and possibly longer. The Saddle Stitch is sewn using one length of thread and is woven through the leather, crossing to either side of the leather at each hole. This stitch is far superior to the lock stitch and can only be created by hand. Even if a thread breaks or is cut the opposing thread will continue to hold the pieces together and will not unravel.