At 118:51:20, while doing final Rover preparations before driving out to meet Jack Schmitt at the ALSEP deployment site, Gene Cernan accidentally caught the hammer he had stowed in his calf pocket under the right rear fender, tearing off the rearward extension. He used grey duct tape to re-attach the fender extenstion but, at about 122:47:48 during the drive back to the LM from Station 1 at the end of the EVA, the tape failed and the fender extension fell off.
Gene and Jack did not stop to retrieve the fender extension and, during the rest period after EVA-1, support personnel in Houston designed a replacment fender that Gene and Jack could make from tape, unneeded maps, and some clamps they had in the cabin. See the discussion at 137:19:09.
A detail from AS17-137-20979 is presented at the top of this page, showing the replacement fender on the Rover just before Gene and Jack leave Station 2. At the time Gene took the picture, the replacement fender had been tested during 9.1 km of driving.
At about 167:41:11, during the drive to Station 9 late in EVA-3, the replacment fender began to fail, perhaps due to the combined effects of prolongted solar heating and the dust and rock fragments thrown against its underside during the total of about 29 km of driving they'd done since Gene installed it.
Later, after parking the Rover east of the LM so that the world could watch LM liftoff with the Rover TV, Gene removed the replacement fender and brought it back to Earth. As of September 2005, it was till on display at the Smithsonian's National Air and Space Museum.