In referring to ' foundation' we describe the basic components of a carpet. These are two in number, namely warp yarns and weft yarns. Usually the same fiber is used for both the warp and the weft and this can be either cotton or wool in handmade carpets. Cotton is most commonly used but wool will be used mostly in places where it is readily available. Silk is used for silk carpets and generally for those with silk piles. Though expensive, silk is highly favored as a foundation material because it is very strong.

Warp

Warp yarns are the vertical strands of fiber stretching from the top to the bottom of a carpet. They are an extremely important component because the knots (if knots are created) are tied to them and the weft yarns are woven through them. Basically if the warp yarns are not of even tension, a carpet will wrinkle.

Weft

From the above you can deduce that weft yarns are the horizontal strands. They are woven through the back and front warp yarns and added before or after the rows of knots, to prevent them from becoming loose.