knob knocker
n.— «“Imagine a razor shaving your face, but on a much bigger scale,” says Shawn McKinney, president of the Springfield Area Mountain Bike Association about the knob knocker, a device created to shave the bumps off a mountain bike trail.» —“Smooth moves” by Chris Young State Journal-Register (Springfield, Illinois) June 26, 2004. (source: Double-Tongued Dictionary)
Further reading
Twice a day the River Thames recedes, revealing a muddy shoreline. Hobbyists known as mudlarks stroll the surface searching for objects that have found their way into the river over the centuries, everything from ancient Roman jewelry to modern...
What if, instead of being an inanimate object, a dictionary were alive? That’s the idea behind a lavishly illustrated new children’s book called The Dictionary Story (Bookshop|Amazon) by Oliver Jeffers and Sam Winston. This is part of a...