Over the years the original name has faded. More and more people today identify such devices as a
steamroller.
According to A Child's Garden of Grass: The Official
Handbook for Marijuana Users (1969,
Jack S.
Margolis & Richard Clorfene) "A steamboat is a combination of a pipe and a joint merging the best of both into a powerful tool of good."
While a true pipe only has two holes (a bowl and mouthpiece), the steamboat has three (a bowl/joint holder, mouthpiece, and a rear hole nearest to the bowl).
To use a steamboat one covers the rear hole, puffs a few times upon the piece to fill the chamber, and then uncovers the rear hole to puff once more - inhaling the full contents of the chamber.
Example:
"Some inveterate critics may claim that these are not
Steamboats, but pipes. They're not. They're Steamboats.
A pipe has two holes, a steamboat three or more."
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A Child's Garden of Grass