When weaving up a swatch of hand spun pineapple fiber, I decided to do a little experiment with twill. In plain weave, the weft yarn alternates going over or under one warp thread all the way across the fabric. Twill goes over or under multiple strands. You can have a pass go over two under two, or over three under one (denim), or any number of combinations. The next pass has the same pattern, just offset by one strand. The resulting twill fabric has a diagonal line going left or right depending on how the passes are aligned.

This was a fun experiment. I rather like twill, and it is definitely something that requires some brain power.