What is a shank button?

A shank button is a type of button that has a small loop-like structure on the back, known as a shank. This shank allows the button to sit slightly away from the garment and provides space for fabric to be passed underneath. Shank buttons are commonly used on heavier fabrics or garments where using a flat button could cause the fabric to pucker or pull. Shank buttons can be made from a variety of materials including plastic, metal, wood, or horn and come in many different sizes, shapes, and colors. They can be sewn on either by hand or machine.