Lay the two corner stock pieces flat, parallel, so their inside corners face each other. Space the corner stock pieces so their inside corners are 28 inches apart.
Set the ribbed aluminum sheet between the corner stock so its 84-inch edges are resting on the inside corners. Position the sheet so its 28-inch edges are flush with the ends of the corner stock pieces. Weld this sheet of aluminum to the corner stock pieces. This is your ramp frame.
Turn the ramp frame over so it is resting on the edges of the corner stock pieces. Position the 28-inch bar against on of the 28-inch edges on the ramp frame frame so its 5-inch ends are flush with the edges of the sides of the ramp. Angle this bar at a 135-degree angle from the ramp frame and weld the bar to the ramp in this position. This is the lip to your ramp, and the bottom of your ramp is facing up. This side will face the ground when it is in use.
Set the lip of your ramp on the tailgate of a truck to load dollies and other equipment into the vehicle.