Knots are another key element in carpet manufacturing techniques. Rows of knots are tied onto the warps in between strands of weft; the first row is bound along the bottom end of the carpet

Example of a carpet made using the Tibetan knot



When knots are tied, the weaver pulls the ends of the yarn downwards. This operation makes the pile evenly oriented, with pile yarn ends all pointing towards the bottom end of the carpet. The pile of each row of knots covers that of the previous row, just the way tiles are placed on a roof. The pile direction can be perceived by observing or touching the carpet. Shading which appears by looking at the carpet from different directions, depends on changes in the weave orientation and how light is reflected by the pile surface. Hence, looking at the carpet from bottom to top, it will appear darker, but from the opposite direction the carpet will appear lighter in colour as the light reflects off the sides of the pile yarn. The design can also reveal what is the bottom and what the top end of the carpet. The two parts are generally indicated by the pattern orientation and are the same as those indicated by pile direction.

There are several kinds of knots.
Carpets are woven horizontally across the loom and from the bottom end to the top end, row by row, alternating weft threads with a row of knots made of colored yarn. The design is created by tying knots using a variation of colours. Weavers sit on a bench, close to each other, and their number varies depending on the size of the carpet. The kind of knot used differs according to the manufacturing area.

The most typical kinds of knots are

The symmetrical knotThe symmetrical knot

In the symmetrical knot, also known as the Turkish knot, the two yarn ends are placed in a loop around two adjacent warp threads and then emerge to form the pile. Looking on the front side of the carpet a loop is noticed passing over the two warps and the two ends of pile protruding out from this loop are also visible.

nodo a-simetrico The asymmetrical knot

The asymmetrical knot, also known as the Persian knot, is wrapped around one warp only, then the yarn is passed open behind the adjacent warp so that the two ends are divided by a single warp. One of the two ends may be open on the left or on the right to form the pile.

In both kinds each knot is tied onto two warps. The asymmetrical knot can be of two kinds: the asymmetrical knot open to the right or to the left.
In the asymmetrical knot the yarn is not woven into the foundation like in the symmetrical knot. On the contrary, it passes around a warp emerging on the right or on the left, depending on how the knot was tied.

The Tibetan knotThe Tibetan knot

Also known as the Nepal knot or cut loop knot, this variety is largely used in the production of modern carpets. In ancient times it characterized only Tibetan carpets, but today it is employed in carpet manufacturing areas of Nepal, Tibet and India.

The Tibetan knot has completely different structure compared to the other knots. This knot is actually made by using a temporary weaving rod along the width of the carpet, which is placed in front of the warp. This height of the rod determines the pile height. The long yarn is then placed around two warp threads with a symmetrical knot and then the end of the yarn which was not cut is looped around the rod. After a row of knots is completed, the weaver presses down the newly tied knots, inserts the wefts, beats them down and finally the loops around the rod are cut to create the knot. At this time the rod is slipped out. This technique delivers a durable and rugged weave. 

Usually the number of vertical knots is higher than the number of horizontal knots. This effect depends from the manufacturing process; after the wefts have been passed to hold the knots in place, the row of knots and wefts are beaten down to obtain the desire tightness and consolidate the weave.