Summarize this article:

\ The second layer of plywood will make your quarter pipe last longer and make it stronger. You don't want to line up the seams of the first and second layer. This is optional.

Summary:
Screw the 2-foot by 8-foot (600 by 2400 mm) piece of plywood you just cut on top of the first layer of plywood at the left edge of the quarter pipe. Screw a 4-foot by 8-foot (1200 by 2400 mm)sheet of 3/8-inch (9 mm) plywood next to the 2-foot by 8-foot (600 by 2400 mm) piece. Screw the second piece of 2-foot by 8-foot (600 by 2400 mm) sheet of plywood next to the full piece to complete the surface. Screw the first sheet of 1/4-inch (5.2 mm) 4-foot by 8-foot (1200 by 2400 mm) masonite onto the second layer of plywood. Screw a second 4-foot by 8-foot (1200 by 2400 mm) sheet of masonite next to the first layer. Make the transition from your quarter pipe to the ground smoother by buying a piece of sheet metal 6 inches by 8 feet (150 by 2400 mm) to screw into the Masonite at the bottom of the ramp.