A style of weaving where the lines of grain run from the top-left hand-corner of the fabric towards the bottom-right hand-corner. Denim jeans that use the left-hand twill have a generally soft and fluffy feeling, especially after washing them.
Also known as an ‘S Twill.’
Usually woven with Z-twist yarn, left-hand twill has a diagonal line running from the upper left to the lower right, like the spine of an S. Preferred by H. D. Lee, left-hand twill creates a softer denim with a more open weave than right-hand twill. Its fading also tends to be a bit more blurry than right-hand twill.
Here is an example of left-hand twill: