It seems that people know about stock prices pinning to devalue expiring options, but do not understand how it could be done intentionally and not as a side effect of hedging. It's really simple. You have an order book with 2 sides. Within a certain time frame, market makers who are not colluding would provide a certain number of asks and bids. To force the stock price in one direction, they simply have to reduce the number of quotes on one side of the book. If they are placing and cancelling orders in nanoseconds, all they must do is select a pattern that on average causes the stock price to pin to the maximum option pain value. It could do this in bursts, or over periods of time when no other orders of significant size are incoming. It can use different strategies to thwart legitimate investor sentiment such as low volume price warps of 10 cents to offset several minutes of a trend, or periods of drifting after large trades. The important thing to know about it is that it is illegal market manipulation and that it requires game theory, a form of automated collusion, between big banking firms.