A little help?

drill a 3/8 hole in there and us a hardened grade 8 bolt with a lock washer and she ain't going nowhere.…. :D
I didn't want to slap you with the big disagreed button there but they're the kind that trail Beast is describing with the screw that goes to the top with a little hole and a big hole. Before I pull out my half inch drill bit and go for it, I'm hoping for a ballpark spot... LOL