Remove the lid from the wood packing crate using the hammer. Insert the pulling end of the hammer under the side of the lid, and press down on the pushing end. This will lift the nails out of the crate and detach the lid.
Hammer the nails up through the lid to remove them. Turn over the lid and use the hammer to pull the nails out of the lid.
Sand the lid and the crate's exterior with 220-grit sandpaper.
Apply a thin layer of polyurethane to the crate and lid using the 2-inch foam brush. This will protect the wood from water damage in the future. Allow the polyurethane to dry completely before continuing.
Measure 4 inches from each corner along one of the long edges of the lid. Attach a hinge at each location using two 1/2-inch screws and the power screwdriver.
Place the lid over the top of the crate, lining up all four edges of the lid with the four edges of the crate. Attach each hinge to the crate at the location in which it rests.
Place the crate cabinet in standing position so the door swings to the left or the right. Continue to create cabinets in the same manner, placing them next to each other until the full cabinet design is complete.