The Essential Guide to Clothing Fabric Swatches – Have you ever received a new item of clothing and found a small square of fabric with buttons in a plastic bag? That’s a fabric swatch, and it serves a useful purpose beyond just providing a replacement button or patch. The primary function of the fabric swatch is to help you test out different cleaning products to ensure they won’t ruin your clothes. This way, you can avoid mishaps when washing and caring for your new garment.