Lets all post variations of Pi Chuan applications or where to find them here. Give the name of the book the author and year it was first published. Same for videos or Magazines.

I'll start.

There are three variations of applying Pi Chuan found in "Hsing Yi Chuan: Theory and Applications" by Liang Shou-Yu and Yang Jwing-Ming 1997 in page 93.

You hit down closed fist or open hand.

If you look at Pi when you start, where the lead hand rolls back into your Dan Tien before drilling up, think about trying to use this movement to wrap around your opponents punching arm, locking it up. Don't think you could "plan" on doing this in a fight, but if you trained it some, it might come out at the right time.

Fan Pi variation: You strike with the back of your hand, instead of your palm.

Getting back to "applications" as opposed to style and techniques...
My teacher taught me to use Pi Quan to break my opponent's collar bone - chopping with the edge of the hand - either fist, or open hand.
Focus your attention and force there.
Not many would think to defend this part of the body... and a broken clavicle basically puts the guy outta the fight!!!! (kinda hard to lift/use his arm anymore)
- from Ma Jun Long, b. 1936, Henan, China

Ps. - Hmmm? maybe this is why I don't have many sparring partners left? ;>)