An arch support is a piece of material designed to provide support for the arch of the foot. An arch support may be placed on top of the shoe's insole, or may be part of the insole.
It is placed inside a shoe so that its molded form fits the arch of the foot. Arch supports are frequently made from plastic, aiming to be flexible enough to provide comfort and rigid enough to provide support. The material can be custom made to fit individual feet using a medical foot casting system. Alternatively, generic shapes and sizes can be purchased based on foot size and arch height.
Arch supports are most commonly found in shoes, but sandals such as Birkenstock are also produced with a degree of built-in arch support.