Raised planter boxes are a good way to utilize a small space for gardening. The advantage of raised beds is that the soil is easily maintained, and can be built up without using soil from your own garden or yard, which may have an undesirable nutrient level. As the University of Minnesota Extension points out, raised beds also provide easy maintenance, as less stooping is required for weeding, and the whole planter box may be walked around without stepping on the planting soil, compacting the dirt.
Measure the area for your planter bed in a spot with good sunlight. According to This Old House, the planter should be 4 feet of width or less to ensure you can reach the middle of the planter without crawling in.
Dig a 6-inch trench for the area in which you will place your timber, and fill the bottom 2 inches with gravel. This prevents the timber from decaying rapidly.
Stack the timbers so that they make a rectangle in the ditch, hitting the timber with a rubber mallet to ensure it is stuck into the ground. Pound two lengths of rebar into each side of the planter base until they are secured in the ground.
Place another level of timber on top of the first layer, alternating the orientation of the timber for a stronger build. Connect the timber pieces together using the 10-inch timber screws. Continue stacking until the correct height is obtained.
Drill holes in the side of the planter box so that water drains from the garden. These are called weep holes, and prevent flooding. Slip copper into the holes to prevent decay.
Miter the lumber edges so that they fit together at a diagonal, and place them on top of your timbers. Smear wood glue on each mitered edge, and place the edges together. Secure the lumber by screwing them to the top piece of timber.
Fill the planter with wood and plants.