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Explanation: "Doublure d'aile", "doublure intérieure d'aile", "coquille pare-boue": protector installed by the car manufacturer, generally plastic, fitted inside the fender to protect the fender against chips from materials sent by the wheel, most often fitted with various plastic clips (1st reference)
"Protecteur d'aile": protector installed outside of the fendre by a mechanic before working on a car, generally maintained by a magnetic stripe, avoids the scratches and possible damage from mechanic's clothes, tools, etc (2nd reference)