The Fence Flapper was an obstacle of the Qualifier. It had flaps on it that swung up, flinging contestants in the mud. Like the Smack Wall Sweeper, the contestants had to try the 2nd half of the obstacle if they failed on the first half. They also had spikes in the mud.
The Fence Flapper appeared in Wipeout the Game for the Nintendo DS and the Wii. It also had a mud pit. When a flap was about to open, smoke appeared from under the specific flap.