BassMechanix 10+ year member
Member
not sure how he did it exactly.
Didn't use a router for that. They have these attachments you can buy that go into your drill, has a handle on it so you drill through then just start to turn the handle... thats why their is a hole in the center. They are really made to cut circles out for cooling fans ext. but like your builder you can get pretty creative with them too.