Clothing alteration services vary based upon the type of garment and the material used. Sewing professionals and people performing alteration services are divided into distinct categories: bridal, couture, custom, costume, leather and suede, and museum or restorations. Specific training is required by each professional to master the techniques used to sew complicated garments by hand and sewing machine. For example: a French couturier will retain a dedicated group of seasoned professionals who know how to drape, cut and alter a garment without ruining the fabric.