The Thule 542 - Artificial Raingutters are for custom applications on fiberglass tops and caps.  The brackets provide four fixed mounting points for the Thule 300 and 387 Gutter Feet, does NOT work with 952 Feet (the blade is wider than the 542 gutter.  The Artificial Raingutter brackets are most commonly attached to the side of a cap, however, the designed to allows for top mounting as well.  The bracket is extruded aluminum and polyester powder coated for strength and long term corrosion resistance.  Rubber pads are included to protect the cap's finish and works in conjunction with silicone to create a weather tight seal.  A steel backing plate reinforces the bracket from the cap interior.  Zinc iron plated steel bolts are included along with nylon insert lock nuts.  See product manual for more details.