View Full Version : Knocker
07-14-2012, 10:09 PM
I am needing to know where I can get something that will knock on the underside of a bridge when triggered by a motion detector. Can anyone help me out with this?
07-15-2012, 08:28 AM
well this isn't exactly a knocker, but years ago we put cheap palm sanders to the underside of our bridge. strapped the corners with "plumbing strap" so they were tight to the bottom. 2 of them worked for a 12ft bridge, we also used a power drill with a piece of "flatbar" welded to a bolt ,chucked inside to slap a door to make it "slam" open & closed..you might could use that same type setup to work.
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