Sentence:  Fabric grids or <WSD>egg crates</WSD>, such as those made by Lighttools, work much the same way for different sizes of softboxes. These <WSD>egg crates</WSD> restrict the direction of the light and how much it spreads across the entire surface of the softbox or subject. 
Meaning of the word marked with <WSD> tags:  A device for restricting the spread of light that fits into the softbox of a diffuser panel.