The straight or running stitch is the basic stitch in hand-sewing and embroidery, on which all other forms of sewing are based. The stitch is worked by passing the needle in and out of the fabric at a regular distance. All other stitches are created by varying the straight stitch in length, spacing, and direction. Running stitches are most often not visible as they are used to close seams. Running stitch, Holbein or double-running stitch, satin stitch and darning stitch are all classed as straight or flat stitches. Backstitch is also sometimes included in this category.