Our dear friend Vassilis notes an easy way to trim ground fills on EAGLE PCBs. This tip is really helpful if you would like to prevent ground to be filled on small areas without having to add a new polygon.
Normally, if we like to add a ground plane on a PCB we use a polygon named GND and then empty space is filled with copper attached to GND net (keepout distance from traces, pads etc can be adjusted). In most cases you will notice that copper is filled in areas that we would not like to be filled. A solution to this is to add a polygon on tRestrict layer to prevent copper to be added on that area. This solution works nice for relative large areas of board.
Another way to prevent ground to fill a small area is to use a wire on tRestrict layer placed in such a way to “cut” the ground filling path. Using such wires on the above PCB give us better results as you can see on the screen below.