Twill fabric has interwoven diagonal patterns. The weaving in a twill fabric is done by passing a filling thread over a warp thread and then under it a couple of times to give the appearance of diagonal lines.
The diagonal patterns can easily be seen in a twill fabric. These twill diagonal lines are formed on both sides of the textile. These lines can be woven in any order from right to left or vice versa. The diagonal patterns make the fabric heavy and durable. Cotton twill is often stiff and voluminous.
This kind of twill weaving is the second major weaving pattern after plain weaving. Cotton is often interwoven with wool to get a heavy twill fabric.