I've done it with maples, never though to try with cannabis.
The very brief summary for anyone maybe interested: air layering is a cloning technique where you leave the clone partially attached to the mother while the roots form. With trees, you do this by cutting away a strip of bark maybe 75% of the circumference of the branch you're cloning. Apply rooting hormone, and then secure a moistened, rooting-appropriate medium around the cut with a plastic bag. Secure bag to branch and wait patiently.
Sounds like it could translate well to our little green friends, I think I might have try this for fun
Edit: and @Kalgrae says "... not so fast" Still might try it on a very lanky probably-male to see what happens.