tack

A tack is a long, loose stitch used to hold two or more pieces of fabric together before they are permanently sewn. The stitches are typically 6 to 12 millimeters long, made with contrasting thread (often a bright color or a loosely twisted yarn) so they are easy to see and remove. Tacking serves as a guide for the final seaming operation and prevents fabric from shifting during handling or machine sewing.

In garment construction, tacking is applied by hand using a needle or by machine at low speed with reduced tension. The thread is not knotted at the ends but rather left loose so it pulls free cleanly. Tacks are placed along seam lines, around hems, and at points where pattern pieces must align precisely, such as armholes, collars, and princess seams. On heavy fabrics like wool or linen, tacks may be anchored with two or three stitches at the end; on delicate fabrics, a single pass of loose stitching suffices.

Tacking is most critical when working with slippery or stretchy materials, including silk charmeuse, bias-cut fabrics, knits, and loosely woven linens. Without tacks, these fabrics will creep during the final seaming, resulting in seams that are visibly off-grain or puckered. Pin basting is sometimes used as an alternative or supplement, but pins can leave holes and do not constrain movement as effectively as thread.

The name derives from the verb tack, meaning to fasten temporarily or in a makeshift manner. The term is also used more broadly in sewing to mean any temporary attachment, though stitched tacking is the formal textile industry usage. In industrial manufacturing, tacking may be done by machine to improve speed, but inspection and re-tacking by hand remains common for high-quality tailored goods and custom pieces.