But which hole does he mean???

Sock, you're going to have to be more specific there.
If you haven't watch the animated project "Welcome to Hell" this joke might be hard to get.
Watch here -> [link]
Anyway, characters go to
My favorite part has to be when Sock is showing Jonathan his "spooky hole". I laughed so hard~ I LOVE THAT ANIMATION, IT'S SO AMAZING TO WATCH