There are a lot of red tags on airplanes that say “remove before flight”. Generally they cover holes that would cause serious problems if they were clogged by debris (like the pitot static system or engine cowlings). Some of them lock control surfaces (ailerons, rudder, elevator) that would otherwise flutter in the wind and get damaged. If it’s part of the emergency exit and the flight attendant’s responsibility, it may be a safety system that they are securing against accidental activation until the doors are closed and locked.
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