I noticed that the inner fender liner on my left front didn't fit properly inside the outer fender -- not surprising, since they are both thermoplastic, but it bugged me. I cleaned the gap between the two, stuck a piece of 3M doubleside auto trim tape between them, then pushed the two parts together, and gently heated the area with a hair dryer for about 15 minutes, then cooled the plastic down, while still holding the bits in place. Problem solved.