Horizontal looms The simplest form of loom is a horizontal; one that can be staked to the ground or supported by sidepieces on the ground. The necessary tension can be obtained through the use of wedges. This style of loom is ideal for nomadic people as it can be assembled or dismantled and is easily transportable. Rugs produced on horizontal looms are generally fairly small and the weave quality is inferior to those rugs made on a professional standing loom. Urbanites are unlikely to use horizontal looms as they take up a lot of floor space, and professionals are unlikely to use them as they are unergonomic. Their cheapness and portability is less valuable to urban professionals. Vertical looms The technically more advanced, stationary vertical looms are used in villages and town manufactures. The more advanced types of vertical looms are more comfortable, as they allow for the weavers to retain their position throughout the entire weaving process. The Tabriz type of vertical loom allows for weaving of carpets up to double the length of the loom, while there is no limit to the length of the carpet that can be woven on a vertical roller beam loom. In essence, the width of the carpet is limited by the length of the loom beams. There are three general types of vertical looms, all of which can be modified in a number of ways: the fixed village loom, the Tabriz or Bunyan loom, and the roller beam loom. The fixed village loom () is used mainly in Iran and consists of a fixed upper beam and a moveable lower or cloth beam which slots into two sidepieces. The correct tension of the warps is obtained by driving wedges into the slots. The weavers work on an adjustable plank which is raised as the work progresses. The Tabriz loom (), named after the city of Tabriz, is used in Northwestern Iran. The warps are continuous and pass around behind the loom. Warp tension is obtained with wedges. The weavers sit on a fixed seat and when a portion of the carpet has been completed, the tension is released and the carpet is pulled down and rolled around the back of the loom. This process continues until the rug is completed, when the warps are severed and the carpet is taken off the loom. The roller beam loom (, "roller loom") is used