Maybe you inherited an old cabinet that has no shelves, or maybe you have a cabinet with shelves but you want to add more. Either way, your home, garage, kitchen or shed will look much more tidy if you maximize the storage space inside those cabinets, especially if your rooms are cluttered with things like crafts, tools, paint cans or canning supplies. Adding shelves is the perfect way to economize the space you already have in your cabinets.
Measure from the inside bottom of the cabinet to the inside top of the cabinet. Divide that by the number of shelves you want. (For example, 48 inches high divided by four shelves equals 12 inches. Note that "four shelves" includes the base of the cabinet, so only three new shelves will actually be added.)
Using the measurement you obtained, mark the height above the inside bottom of the cabinet in all four corners. Continue marking multiples of that height above the bottom of the cabinet in all four corners. (For example, 12 inches, 24 inches and 36 inches.)
Cut 1- by 2-inch lumber to fit all lines on the left, right and back walls. Hold these wood braces flat against the walls of the cabinet so that the top edge of the lumber follows the lines. Drive 1-inch wood screws through the wood braces and into the cabinet walls. Insert one screw every 6 to 8 inches. If the cabinet walls are too thin to hold the screws, then drive the screws from the outside of the cabinet through the cabinet walls and into the wood braces.
Draw a level line along the left, right and back walls between each mark, using a straight edge. Note that this line marks the top of the shelf support; the actual shelf will be ½ inch higher because of the thickness of the plywood.
Measure the size of each shelf and cut plywood or particle board to fit. Slide each shelf into position and fasten with screws, driven from the top down into the wooden braces.