Windless and windlass are very close in spelling, but worlds apart in meaning.

Windless simply means without wind or calm. It is more often used to describe a lack of wind when some wind would be helpful. Sailing vessels must use auxiliary power on windless days, such as oars, poles or a motor.

Comparison of a differential pulley or chain hoist (left) and a differential windlass or Chinese windlass (right). The rope of the windlass is depicted as spirals for clarity, but more likely helices with axes perpendicular to the image.

Comparison of a differential pulley or chain hoist (left) and a differential windlass or Chinese windlass (right). The rope of the windlass is depicted as spirals for clarity, but more likely helices with axes perpendicular to the image. (Wikipedia)

A windlass is similar to a winch and provides lifting or pulling power by turning a rope or chain around a horizontal drum, converting rotary power into linear motion. Such devices can be found in car repair shops and are called motor or engine hoists. These are called differential windlasses and use two drums (as in the picture above). The main point of a windlass is to create a geared lifting or pulling device which enables the lifting of heavy objects by hand, or by using motors. 

It was by the use of windlasses that heavy stones were lifted into place onto medieval church spires and heavy anchors were lifted back onto the deck of a ship. Simpler windlasses with a single drum made lifting the water bucket from the well much easier.