The different types of knots can be used to place the rug's geographic origin as well as to determine the appearance of the pile, or lack thereof. It is important to remember that not all rugs have piles; those that do not are called flat weaves. The two most common pile knots are “Symmetrical” and “Asymmetrical.”

The Asymmetrical or Persian knot is formed by wrapping the yarn around one warp strand, then passing it under the adjoining warp strand and then bringing it back to the surface.  This type of knot, also known as the Senneh knot, produces a finer weave.

The Tibetan Knot is a distinctive rug-weaving technique. A rod, which establishes the length of the 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, the weaver cuts the loops, thereby freeing the rod and creating the pile.  

The Symmetrical or Turkish knot is formed by wrapping yarn around two adjoining warp strands and bringing it to the surface in the middle of the two strands.  Turkish and Kurdish tribes of Turkey, Iran, and the Caucasus use this type of knot, also known as the Ghiordes knot. The Turkish knot is sturdier than the Persian knot but produces a less fine weave.

Additional knots are also used in rug
weaving.  The Jufti knot or "false" knot
can be either Persian or Turkish in style. 
This knot is usually tied over four warps
instead of the normal two - making the weaving process faster.  Even though this technique uses half the material and only takes half as much time, it will probably last only half as long!

Knot density is the measure of knots per unit area of a rug. Knots are counted vertically and horizontally within the given area along the back of the rug. Knot density is affected by many factors like the size of warp, weft, and pile threads, the presence or absence of warp depression, and how tightly the weaver “temps,” or packs down, each row of knots. Knot density is important because it can determine the quality of the rug. The more knots per unit the rug contains, the higher the quality

Grading knot counts:

            •           Course: Up to 25 knots per square inch

            •           Medium: 40 to 90 knots per square inch

            •           Fine: 90 to 166 knots per square inch

            •           Very Fine: Over 167 knots per square inch