Pop Up Warning Sign - Bikes on Roof

Tired of forcefully taking your bike off of your car's roof rack by driving it into your garage door? This aims to put an end to decapitated bikes everywhere. Sign mounts to your car's hood with magnetic strips. When traveling at speed, air moving over the car folds the sign closed. At low speeds or when stopping, springs pop the sign open, offering up a reminder that your bikes are still on the roof.

Additional parts needed (with links):

(3) 7/8" long, 1/8" diameter dowel pins
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