Thats what I am doing. Putting a piece of heavy pipe in a big tin mail box.

We used to take off from Pullman on long fishing trips while in college. We would load up the floor boards with big round rocks about half the size of a bowling ball. We would bomb down the highway and hold the rocks out the window and just drop them into a mail box at 90mph. The boxes would just dissapear leaving the post intact. One time we got pulled over for speeding. The sheriif wanted to know why we had all these rocks in the car. We made up some story about using them camping. He asked us if we knew antything about mailboxes being stolen in the area?