Pre-existing holes for the mud flaps in the wheel well or for the board brackets in the underbody? The underbody has spots where the board brackets bolt up to. For factory boards that is... The front ones are actually accessible from the interior of the cab. Pull up the front carpet and there are plastic caps which cover the bolt heads. The mudflap screws can be drilled directly into the wheel well. At least thats how mine were and they were factory installed (before anybody decides to disagree

).