I have made a black solid and added a generated grid to it. I pre-composed the layer and pasted the mask on the layer below on the solid layer. The mask has not removed the outside contents, but the mask is present. The grid should be in the shape of the mask, but that hasn't happened. Is there a setting which I have to turn on for that mask to work or something? I copied something from a youtube tutorial which worked fine on there, so there must be some sort of setting I need to change? If anyone could help me, that would be great thanks!
Well, you missed a step haven't defined the masked shape as a matte for the grid...
ah. How exactly do I do that? I've also just tried to mask something else, literally just masked something out of a clip with no solid over the top, and it hasn't dissappeared.