This is an extension I built to extend the distance of my plug-in box from the wall. When they put stucco on my shop I needed to bring the plug in out almost an inch and a half. This slips in to the existing receptacle snugly and then you screw your plug into it sandwiching it all together with extra long screws. I threw a little glue on the seam as well to prevent moisture issues.

So far so good.

I even printed it in some blue that I had that exactly matched the color of the box.