Decora No. 12 thread It is a decorative serger thread used to embellish seams and create decorative overlock treatments for apparel or home décor projects. It is also great for quilting! Made of 100% rayon, this thread has a high tensile strength which allows high stitching speeds like those of embroidery machines and sergers. Decora thread has a beautiful high sheen for the perfect stunning stitched embellishments!