Lay four 2-by-4-inch boards on the floor, parallel, with the broad side facing up. Space the boards so they are 2 feet apart from each other, measuring from the center of each board. The total distance from the first board to the last is 6 feet.
Lay two 6-foot-2 by 4-inch boards on top of the first four boards, perpendicular to the first boards, and spaced so that each board is two feet from the respective ends of the first set of boards.
Nail the boards together, using 10d sinker nails and a hammer.
Repeat Steps 1 through 3, creating an identical frame of 2-by-4 boards.
With the help of an assistant or two, raise each structure to vertical, standing on the ends of the four parallel boards. Arrange the frames so they are parallel to each other and separated by 10 inches.
Slide the 1-by-10-inch boards into the space between the frames, resting the edges of the boards on the tops of the boards that are parallel to the ground. Nail the 1-by-10 boards in place with 10d nails and a hammer.
Position the shelves in the desired location.