Why is a tree or an American flag sometimes placed on the highest part of a building under construction?

   A tree or flag placed on, or nailed to, the highest part of a building under construction is a modern version of the ancient "topping out" ceremony. Topping out, still practiced in many parts of the world, is meant to indícate that the frame of the structure has been completed. During a topping out ceremony of long ago, a barrel of beer might be drunk while a tree or wreath was attached to the ridge of a building's newly completed roof. Today, finishing the frame of a building is still cause for celebration.