Many bumper covers, like the rear bumper cover of this Mazda Miata, feature welded-in reinforcement brackets. These reinforcements are secured by tabs in the bumper cover that pass through slots in the bracket and are then melted over like a mushroom. In this case, the reinforcement bracket has become detached from the bumper cover. Since both parts are made of the same plastic material (polypropylene), a nitrogen plastic welder can be used to fusion weld them together.