O/T How to make a howler? (practical joke)

[exohuntr]

I have some club members that like to play practical jokes, so I want to deliver some payback. Have any of you ever heard of a howler? It was a noise maker made out of a big can. My old boy scout leader used one to scare us to death on a camping trip when I was younger, and it made a sound like nothing I have ever heard before. I need to know how to make one. Best I can remember it was an old can that he pulled a piece of leather through to make it howl. Any help would be greatly appreciated, or if you have any ideas for fun payback I am all ears... exohuntr