Call Wall Strike is the strike with the largest net positive gamma in the underlying stock. 

Why does Call Wall Strike matter?

This strike signifies where investors are targeting the top side of a bullish range. 

How to use Call Wall Strike

This level is considered a major magnet/pinning area for markets, and a major resistance point. When this strike is rolled higher it is generally considered bullish, when it moves lower its considered bearish. Please see a full article here.