Blind stitch Wikipedia
A blind stitch in sewing is a method of joining two pieces of fabric so that the stitch thread is invisible, or nearly invisible.
There are several techniques for creating a blind stitch by hand sewing. A common technique used to create a hem, or "blind hem", hides the stitches on both sides of the garment. The sewer catches only a few threads of the fabric each time the needle is pulled through the fabric. Other techniques hide the stitch within the folds of the fabric, so that the thread is only visible when the folded material is pulled away. A slip stitch or catch stitch can be used to create the blind stitch, except that they are worked inside the hem, 1⁄8 to 1⁄4 inch (3.2 to 6.4 mm) away from the edge of the hem fabric.
A sewing machine can also create a blind hem. In this case, a specialty presser foot is needed. A zigzag stitch technique may be used with a sewing machine to create a blind stitch.