Symmetric and asymmetric knots, as two original knots, possess different physical and mechanical properties that influence the function of a carpet. Jufti and U knots give different properties to the carpet compared to the original ones. If they were used to produce specific properties, they would enhance the carpet's quality. However, nowadays their applications are considered as methods that diminishes the quality of carpets. As these properties have significant influence on the carpets, some attention is paid to them in different papers and textbooks. Carpet samples are woven with each knot type and identical materials by a weaver. Then the effect of various kinds of knots measured on the carpet length, carpet thickness and pile height. Samples are woven in two different methods. The first one is a method in which the number of beating the comb is controlled; i.e., after each row of knots only and exactly two comb beats are applied to the row of knots. In the second method, the dimensions of samples were controlled and it is tried to weave the carpet with the dimensions designed; i.e., the number of times the comb is beating down the row of knots varies according to the weaving progress. In jufti and U knot samples, the number of beating times inevitably reduced to one, while in symmetric and asymmetric samples it increased to five to six times to obtain the designed dimensions. Results show that symmetric and asymmetric knots lead to an increase in the carpet length, whereas the other two knot types end in a decrease in the carpet length. To reach the designed length it is necessary to change the number of beating or to use different materials with suitable yarn counts. The thickness of the foundation of carpet is also influenced by the knot type; i.e., if the number of comb beating increases the foundation thickness increases as well, but if the number of comb beating remains constant there will be identical foundation thickness in carpets woven with different types of knots.
