[CSXDreamer]

Most door jambs are double 2 X 4s or 2 X 6s, mainly for vertical frame strength. Then the carpenters lines the opening with shimmed 3/4" thick pine or spruce boards. This is what the hinges and catch for the door lock are screwed to. I think TV shows are very accurate when they show a 200 lb. actor kick a door in or hit it with a shoulder. The screws just split the wood. Use longer screws into the framing, it just takes a couple more whacks. If you watch a karate guy show off breaking boards, he's using pine, which splits very easily. Think about what would happen if someone snuck in an oak board!