The windlass is that device which are used by the mariners on yachts to wind the rope around to help to make it easier to move the sails. In the foot there is a mechanism that is referred to as the windlass mechanism that gets its name from this equipment used on boats. There is a ligament like structure under the foot called the plantar fascia that is at one end connected to the underside of the heel and at the other end to the great toe. When we are walking and the heel bone comes off the floor, the foot rotates around the great toe or hallux where this ligament is attached, tensing the ligament as it winds around the windlass of the first metatarsal head. This is the windlass mechanism of the foot. It is a crucial function as the plantar fascia is what supports the arch of the foot, therefore it is required to function properly and efficiently for normal biomechanics. This is the foots natural arch support mechanism.
There are a number of conditions related to this windlass mechanism not functioning correctly. If the windlass doesn't work, then the arch of the foot will collapse from this lack of support and a variety of conditions can develop as a consequence of that for example bunions and plantar fasciitis. The explanation for the windlass not working correctly can be multiple like the force required to establish it just being too much, so the body has to work harder to make the windlass function. If that effort does make it work, then that is an increased energy expenditure which can be very fatiguing. Podiatrists use different design features in foot orthotics to improve the windlass mechanism and to make walking easier and more effective. In the event the windlass can be established easily when walking will not require very much and the foot can naturally support its own arch.