The term FASTENING OPTION can be summarized by the crossword solution STRAP, which is a five-letter word. A STRAP is a type of fastening option that is used to secure items together. It is usually made of a flexible material such as leather, fabric, or plastic and is often used in conjunction with buckles, clips, or other fasteners. Straps are commonly used to hold luggage, backpacks, and purses closed, and they are also used to secure items to vehicles, walls, and other surfaces.