How To- Waterproof Rooftop Storage Boxes Securely Mounted On A Roof Rack

How to install waterproof storage box on roof rack for overlanding. Quick release rooftop cargo box on a Toyota 4Runner, but they can also attach to aftermarket roof racks on a Tacoma, Jeep, Subaru, truck, anything with a flat crossbar. We use large Plano gun cases, or rifle case, but any plastic or aluminum gear bin can be mounted the same way. Our DIY method mounts an inexpensive waterproof storage case securely and safely to our roof rack bars.
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Items below were sourced from McMaster-Carr: https://www.mcmaster.com/

6- 92311A544
18-8 Stainless Steel Cup-Point Set Screw, 1/4"-20 Thread, 1-1/4" Long.
1- 7062T23
Multipurpose 6061 Aluminum Z-Bar, 1/8" Wall Thickness, 1-1/8" High, 1-1/8" Outside Width, 3 Feet Long.
1- 1466N32
High-Temperature Silicone Rubber Strip with Adhesive-Back, 1" x 36", 1/16" Thick.

Items below were sourced from Amazon:

6- 80/20 Inc, 3686, 15 Series 1/4-20 Centered Slide in Economy T-Nut: https://amzn.to/3k9dKHy

1- Lee Engineering Aluminum Lab Frame Lattice Rod 1/2" Diameter X 36": https://amzn.to/3drLiPU

1- SBDs (Pack of 10): 1/4"- 5/16" Round Black Vinyl Flexible End Cap Bolt Screw Rubber Thread Protector Safety Cover | for 0.250 Inch Pipe Post Tubing Rod OD Cover - 1" inside Height: https://amzn.to/3auyZjN

2- Plano Mil-Spec Field Locker Tactical Long Gun Case with Wheels: https://amzn.to/3pyHLBE

Items below were sourced from Lowe's:

8- 1/4" 20 x 1" stainless steel bolts
8- 1/4" 20 stainless steel nylon lock nuts
6- 1/4" 20 wing nuts
1- 1/16" x 1" x 3' aluminum flat stock
1- 1/8" x 1 1/2" x 4' aluminum flat stock

Pulled out from under our workbench:

An old rubber semi trailer mudflap.