The windlass is that gadget that are used by the sailors on yachts to wind the rope about in order to make it less difficult to move the sails. In the foot there exists a mechanism that is called the windlass mechanism that gets its name from this apparatus used on boats. There is a ligament like structure under the foot known as the plantar fascia which is at one end attached to the bottom of the heel and at the other end to the great toe or hallux. When we are walking and the rearfoot comes off the ground, the foot moves around the big toe where this ligament is connected, tightening the plantar fascia as it winds around the windlass of the first metatarsal bone. This is the windlass mechanism of the foot. This is a vital functionality as the plantar fascia is what supports the arch of the foot, so it really should function correctly and efficiently for normal biomechanics. This is the foots natural arch support system.
There are a number of conditions involving this windlass mechanism not functioning effectively. Should the windlass mechanism does not work, then the arch of the foot will fail from this lack of support and a variety of disorders can develop because of that such as bunions and heel pain. The explanation for the windlass not functioning correctly can be multiple such as the force required to establish it just being too much, so the body has to work harder to make the windlass work. If that hard work does make it function, then that is an increased energy cost that may be very fatiguing. Clinicians use different design features in foot orthoses to facilitate the windlass mechanism and also to make walking less difficult and more effective. In the event the windlass can be established easily during walking or running won't require so much and the foot can naturally support its own arch.