Open Interest walls or OI walls are similar concept to max pain. Both rely on the option writer, which is the market maker, hedging the options he wrote.
For max pain, you use the cash value at each strike to see where the option writer should lose the least amount of money. You expect his hedging activity to drive the stock price to that point.
OI walls are different in that they provide a range of possible values for the close. For example, consider the following chart.
The max pain strike price is 320. A close below 320 means that 1,800 put options at 320 would be in the money. Similarly a close above 320 means some 1,800 call options at 320 would be in the money.
The OI walls are at 300 and 330. The 300 strike has the highest number of puts at 2,800 contracts. The 330 strike has the highest number of calls at 2,600 contracts.
Should the stock price move toward the 330 price, the option writer / market maker would be paying out on a significant amount of calls. He will rebalance his hedge in the common stock to compensate. That rebalancing will apply pressure to keep the stock below 330. So the 330 strike can thought of as a "wall" that the stock should not move past.
Should the stock price move dramatically toward the 300 price, the same thing will happen. In fact, looking at the large number of puts all the way from 320 down to 300 there should be more pressure to keep the price above the 300 than below 330.
For this example, the OI walls are predicting a close between 300 and 330. AMZN closed at 311.39 on Friday 10/10/2014. This is within the OI walls.
The benefit of using OI walls is that it has a higher probability of success than max pain. Max pain is predicting an exact close. OI walls says the close will be within a range of values.
How can you use this to your advantage? The iron condor is an option strategy that relies on the stock price to remain within a range. The OI walls can be used to define what range the stock will remain in. You can establish the iron condor on these values.