Our kegerators used to come with just 1 hole to feed the beverage lines through. Since there are different tower options available, we'd send the draft beer tower and other components along with 3" screws so that the tower could be custom mounted.
Now, our kegerators come with pre-drilled holes and require shorter length screws. Rather than 3" screws, 1" screws are now used.
You'll need 4 - Machine Screws, Flat, Stainless Steel, 10-32x1"
These can be found at your local hardware store, or you can pick some up here.