Raised planter boxes provide homeowners many advantages. These increase garden space, allow gardeners with limited mobility or back problems to grow plants or flowers without bending too low, and protect the plants from ground pests such as rodents and weeds. Use cedar boards (that are naturally disease and rot-resistant) to create a rectangular raised planter box that measures 10 feet long, 3 feet wide and 12 inches high, or alter the measurements to fit your requirements.
Measure and mark two 3-foot lengths on the 6-foot-long 1-by-12-inch cedar board. Cut over the line with a circular saw so you have two identical boards measuring 3 feet long. Sand the edges to make them smooth. These boards will form the short sides of the raised planter box.
Place a 10-foot board on its narrow edge over a flat surface. Also place a 3-foot board on its narrow edge at a right angle to the longer board, ensuring that they form a corner and that the joint is flush and even.
Drill wood screws that penetrate both of the boards to join them together to form an L-shaped structure.
Place the corner of the second 3-foot board flush against the corner of the other 10-foot-long board at a right angle so they form an even joint. Join both of the pieces with wood screws so you have a second L-shaped structure.
Align both of the L-shaped structures so the 3-foot board of one corresponds with the 10-foot board of the other, creating a rectangle. Make sure both joints are flush and even before joining the structures carefully with wood screws so they form a rectangle cedar planter that is 10 feet long, 3 feet wide and 12 inches high.
Measure and mark a 45-degree angle at one end of each of the four wooden stakes. Cut over the mark with a circular saw to create a sharp pointed edge on each. Place a wooden stake in the corner of the planter so its pointed edge rises 6 inches over the top, and secure it with wood screws. Repeat the same procedure for the other three corners.
Lower the planter over your desired location with the pointed edge of each stake inserted in the ground. Pound each corner with a hammer gently to secure the raised cedar planter in the soil.