Make a grid only appear on top another of another object

Make sure the shapes that make up the grid are grouped.
Now there are two ways you can "mask" the grid in the shape of the circle. Just depends on how many shapes you want to maintain.



1) Start with the circle placed on top of the grid. Duplicate the circle and move the copy out of the way. Then select the original circle and the grid group and press ctrl+7 (command+7 on mac). That will mask the grid but it removes the fill and stroke from the circle which is why we duplicated it first. Deselect everything and with the open selector (white arrow) click the now colorless circle. (You may need to jump over to wireframe mode real quick to see the circle. ctrl+y will toggle between artwork and wireframe mode). Now grap the eyedropper and click the copy of the circle to get the color back.

2) Start with the grid on top of the circle. Select the circle and copy it to the pasteboard (ctrl+c). Now lock the circle (ctrl+2). Paste a copy of the circle on top (ctrl+f). Select the copy and the grid and hit ctrl+7. Unlock the original circle (ctrl+option+2)

Method 1 has less shapes but takes more steps. Method 2 has more shapes to maintain but is relatively painless.

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