A style of weaving where the lines of grain run from the top-right hand-corner of the fabric towards the bottom-left hand-corner. The right hand twill is the most common twill used in denim.
Right hand twill is the traditional weave used for jeans and was the type of fabric that Levi Strauss first bought for his pants. It is usually woven with S-twist yarn with a diagonal bias running from the upper right to the lower left, like the spine of a Z.
Right hand twill creates a tighter, more compact material with a crisper fading pattern to it than left hand twill.
Here is an example of Right Hand Twill: