Felt is a layer of wool fibres, wet with water as a lubricant, sometimes with some soap. It is crushed together by repeated compression.
The most common method of compressing the wool is rolling; with bare forearms or feet or using a rope. Sometimes a bundle is also tied around a pole which is then pulled by a horse. The latter method is the most frequently used in Mongolia, western China and other areas.
Heating can speed up the process of felting.
The frequent use of felt is undoubtedly due to its simple method of production and its flexibility. It can be modelled into reasonably stiff, utilitarian purposes such as making hats and boots, as well as into thin sheets that can be used, for example, as rugs or to cover nomadic tents. Patterns and colours can be integrated during the rolling process or later pieces from different sheets of various colours are sewn together.