• The Call Wall is the strike with the largest net call gamma. 
• This is one of our most important key resistance levels. It holds a majority of the time.
• Call Wall are essential in our daily levels analysis.
• Their main function is that they define the upper bound of the wider probable range. 
• The direction that walls shift overnight is a strong directional signal: up equals bullish and down equals bearish. This is often what we are keeping the closest eye on while waiting for a bullish signal from the market. 

For further study on Ball Wall GOTO >>> SpotGamma