Fabric alone cannot hold thousands of tight stitches without distorting. Backing, also called stabilizer, gives it a firm foundation. The two everyday types are cutaway, which stays permanently behind the design and is trimmed around it, and tearaway, which is torn off after stitching. Wash-away backings dissolve in water, and a thin water-soluble topping laid over towels, fleece or piqué stops stitches sinking into the pile.
The fabric decides the backing. Stretchy knits such as tees, polos and sweatshirts generally need cutaway, because once tearaway is removed the stitches have nothing holding them as the fabric moves. Stable wovens and caps often use tearaway. Backing weight is matched to how dense the design is.
Cutaway leaves a patch of soft material inside the garment, which some wearers notice on thin tees. Ask which backing the shop plans for your garment and whether a soft cover backing over the inside of the design is available. See how embroidery works.