A planter is an enclosed box filled with flowers, plants or herbs and placed anywhere, either indoors or outside. A deck railing planter is functional and decorative, because it provides gardeners the advantage of growing plants of their choice without bending too low. It also adds color to your deck, which is a welcome sight for people relaxing there or for those on the street, and can be used as a privacy screen when placed strategically. Follow these steps to build a 3-foot-long and 6-inch-deep planter, or vary the size to fit your deck railing.
Purchase rot-resistant cedar boards from your local hardware store, or cut them yourself with a handsaw. You need five boards--one 3 feet long and 8 inches wide for a base piece, two 3-foot by 6-inch boards for the front and back of the planter and two 6-by-6 pieces for the sides.
Sand the edges to make them smooth.
Assemble your planter by placing the base piece on a flat and even surface. Hold the front piece against it, making sure the joint is flush and even. Attach the two boards together by drilling 1-inch woodscrews. Check the structure to make sure it is secure, and then repeat the same procedure to attach the back piece to the base.
Lower one of the side pieces into a cavity and attach it to the base first, and both the short edges of the front and back, using 1-inch woodscrews. Repeat the process with the other side piece.
Check the stability of your planter box. Make sure all the joints are firm and secure, and the box does not wobble. Reinforce any weak joint by drilling another screw. You do not want it to fall apart due to the weight of the soil and plants it will contain. You now have a 3-foot long, 6-inch deep and 6-inch wide cedar planter box.
Turn the planter box upside down so the base faces upwards. Drill 1-inch drainage holes into the base, spaced 6 to 8 inches apart.
Sand the box again to remove any splinters or sharp edges, and give it a smooth finish. It will also help the paint adhere to it. Apply clear or colored exterior paint to your planter to protect it from natural elements and enhance its appearance. Allow it to dry thoroughly before attaching to the railing with woodscrews.