If you are building your own custom router table you are likely using a wooden counter top for the work surface. A router lift will always have leveling screws that contact the wood surface, but unfortunately they can degrade the wood over time. By adding this insert between the wood and the router lift leveling screws your wood will never degrade and your custom router table will last for years! (Router lift not included) 
 
To cut the hole in your router table surface with this template we recommend this bit and that you use this template. 
 
See how to use this product in this instructional video.