Dress up your outdoor space with rectangular cedar railing planters. Cedar is a softwood that is easy to manage for home projects and is naturally rot- and decay-resistant. Making a cedar planter yourself is cost-effective and enables you to customize it to your needs. Fill your planters with your favorite tall or cascading flowers or foliage to enjoy the rich burst of color. Mount the railing planter strategically to increase privacy on your patio or deck when you lounge there.
Measure the width of the railing. This measurement will help you determine the size of the planter. Ideally, it should be as wide as the railing, up to 9 inches deep and up to 3 feet long. Increase the depth if using the planter for privacy purposes.
Cut five 1-inch-thick cedar boards according to your measurements. You will need two equally long and wide boards for the planter's front and back, two equally short and wide boards for the sides, and a bottom board that is as long as the front and back but as wide as the sides.
Hold the front of the planter to a sidepiece firmly so that the joint is flush. Drill a row of three galvanized wood screws over the joint to attach the pieces together. Repeat the process to attach the other sideboard to the front of the railing planter.
Hold the planter's back piece against the edges of the short sides so that it is parallel to the front. Make sure both the joints are flush and the tops are at the same level before securing the back panel with wood screws.
Turn the structure over so that the lower edges of the four assembled boards face upward. Carefully place the bottom board over the edges, aligning it so that it rests on them evenly. Drill it into place with evenly spaced wood screws, three per short side and six to eight per long side.
Drill 1-inch drainage holes into the base of the railing planter, spaced evenly apart. Drill the holes in rows or evenly space them throughout. Sand the surface around the holes so that it is smooth.