Felt belongs to the group of non-woven textile materials. It is possible to suggest that felting is one of the most ancient textile technologies. Very likely that it appeared due to practical observations of our ancestors. They might notice that after some time wool used as spreading got new qualities while being wet and felted. It became thick entire material, also warm and light.
Principle of felting is simple. Maybe you have seen its result on wool sweater after its washing in laundry washer using too hot water. Process was uncontrolled in that case and sweater is spoiled.
It is necessary to put in layers according to the form of needed product well-carded wool in order to get felt. You should remember that during the process of felting size would get twice or thrice smaller. Wool is poured with hot suds and carefully rubbed. After some time you may notice that strands of wool do not sprawl out under your hands. Now you can work more actively. Half-finished product can be pressed, squeezed, rubbed and rolled till the needed thickness. For example, for making coating for yurtas (nomad's tents) people often use horses.
Archeological finds of remains of ancient cloths show that felting was not used only as an independent technology having as a result new material felt, but also in combination with others. Felting of wool things made by needle binding or weaving is also common.
Woolen cloth is well known for its thickness, high ability to save warm and not be venting. It is made by felting of wool woven material. In some period of history owners of cloth manufactures were really powerful.
There are several methods of felting cloths. Felting in mortar doesn't need any special equipment. In culture of Scandinavia there are special songs that were sang during this long process.