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Very cool. That trip mechanism is really neat. So as Bob said, is this what is considered a perch trap? I had heard the term, but never seen one before.
You could use them for what ever you want but I considered them a change, and the wind blows the flag around just enough to keep the bait moving. Mine are very sensitive. If it's real windy, I slide the felt part of the flag down on the tripper wire, so I don't get many wind flags. Here a pic. of mine, very crude compared to the workmanship of the ones Gary posted. Also, I think that forsner bit will make a nice set hole?
if you set that up with the flag not connected over the hole and lay your line over the flag itself and down the hole, it makes for an extremely sensitive crappie trap. you can see the slightest hit