Extra space in the body voor a pickup
Here is an example of an extra cutout that was made in a Fender Mustang body. As you can see, the hole was filled up with a block of wood afterwards. After that, the original pickguard with accessories was put back and nothing is visible on the outside of the mutilation.
At the bottom an image of a Gibson Marauder, in which a scar can be seen between the bridge and the pickguard. Wood was later removed under the body to refill the hole afterwards, so that the color and pattern of the repaired part neatly matches the rest. The seam and one of the filled holes are not even noticeable at some distance.