One end of the pile wool piece comes up between the two warp threads and the other end comes up on one side of the two warp threads. This is also called the"asymmetrical knot." The asymmetrical knot is used in Iran, India, Turkey, Egypt and China. To form this knot, yarn is wrapped around one warp strand and then passed under the neighboring warp strand and brought back to the surface. With this type of knot a finer weave can be created.
Also called the "Ghiordes or symmetrical Knot." In this knot, the pile thread is looped under both warp threads and come up between the two threads. The Turkish knot viewed from the pile side will appear as a short thread across both pile threads The symmetrical knot is used in Turkey, the Caucasus and Iran by Turkish and Kurdish tribes. It is also used in some European rugs. To form this knot, yarn is passed over two neighboring warp strands. Each end of the yarn is then wrapped behind one warp and brought back to the surface in the middle of the two warps.
The jufti knot can be seen in rugs of Khorasan, Iran. This knot can be either symmetrical or asymmetrical. The knot is usually tied over four warps making the weaving process faster.
In Tibet, a distinctive rug-weaving technique is used. A temporary rod which establishes the length of pile is put in front of the warp . A continuous yarn is looped around two warps and then once around the rod. When a row of loops is finished, then the loops are cut to construct the knots.
Single Weft: is called "Sennah Baft" or Hamadan weave. Here the wefts are rigid and the warps are sinuous. As you can see in the sketch the wefts are heavier than the warps. It is woven with symmetrical knots. Since there is only one shot of weft between each row of knots this shows every other warp which makes these rugs easy to spot. A "Single Weft" carpet means that after a row of knots is tied; the loom pedal (shed) is operated - separating alternating rows of warp threads. The weft thread is passed from one side to the other. Another row of knots is then tied and the loom shed is reversed and the weft is passed back through. This results in a single weft thread between each row of knots. In these carpets, the warp threads will be visible.
A "Double Weft" carpet means that after a row of knots is tied, the weft thread is passed through, the loom reversed, and the weft is passed back through. The wefts are then pounded down to lock the pile. On a double weft carpet, one cannot see the warp threads. In older pieces, three wefts between rows of knots was common, and in certain tribal pieces, 5 or 6 weft threads can be seen between the rows of knots. Sometimes, in double weft carpets, the alternating wefts are often made of different thickness, with the heavy weft being drawn tight and the lighter weft inserted with less tension. This has an effect of setting alternating warps in different planes resulting in longitudinal ridges on the back of the carpet. This effect produces a carpet that feels much stronger.