Back-stitching by hand
This is the strongest of all hand-sewing; nowadays it’s only used for short seams or for improving seams where it’s not worth setting up your machine. Work from the right side of the fabric and from right to left. Insert needle, exit about 5 mm further on. Insert needle about 3 mm behind needle exit and exit after double stitch length (about 6 mm). Insert needle exactly in previous exit point and insert again after double stitch length and so on.