The Komoku of the Chinese Opening
While browsing the first chapter of The Chinese Opening, written by the late Kato Masao, I finally understood the proper use of the komoku (3-4) stone in the Low Chinese Opening.
Black actually wants White to approach this stone, and preferrably with a low keima. It's a trap. White can and, most likely, will live. Black, however, will make living a painful affair and will build both points and a huge moyo while chasing White.
Coincidentally, on the evening of that same day, I had a game on IGS where my opponent made exactly that approach and I applied Masao's guidance of immediately attaching to the approaching stone.
If you've ever used Hiroki Mori's interactive Go tutorial, then the interactive diagram with the full opening sequence will be visible to you below. It's the GoodShape Applet and one of his creations. The buttons will allow you to navigate through the moves. The board is also clickable in case you would like to experiment with some variations of your own.
(And, of course, if it doesn't work, please let me know about it and inform me which browser/OS combination you're using.)