Twill Weaves are better at handling compound curves than plain weaves. Look closely at the diagrams and you'll see the way the weave is formed. (The twill is formed when the weft passes over warps 1 and 2 and under warps 3 and 4, and in the next pass, the shuttle of the loom passes over warps 2 and 3 and under warps 4 and 5.) There are many variations on the theme so you will see twills listed as 1/2, 2/2, 1/3, etc. Twill fabrics are characterised by their appearing to have diagonal lines running either right or left on the fabric face.The first advantage is the fewer number of times the fibres go under and over one another. A variation of the twill is the Crowsfoot or cross twill. Twill weaves feel generally tighter, or more closely woven, than plain weaves. For most purposes a nice 100 - 160gsm twill is the best choice. (German Twill = Köper.)