If you want a clear and visible boundary to your garden, building a garden border is the best way to go. This keeps the grass and weeds out, while keeping the plants and scenery organized. You can use many types of material for a garden border, each with its own uniqueness to fit the personality of the yard. The example here uses a simple lumber border, which is one of the easiest to construct.
Dig a trench around the garden with the shovel. The trench will need to be 3 inches deep by 3 inches wide to comfortably fit the boards into position. The width allows you to work with the boards, while the depth will be enough to hold the boards and gravel in place when the garden border is complete.
Place a 1-inch layer of gravel along the bottom of the trench. This will help drainage, keep out boring insects from both the boards and the garden, and keep the border from rotting.
Coat each plywood two-by-four with the weather sealant, using the 2-inch brush. Cover the board completely. Allow the boards to dry before placing them into the ground. You do not need to coat the boards a second time because they are going into the ground.
Place one of the two-by-fours lengthwise into the trench so that the 2-inch side faces up. Make sure half of the board is above ground. This will keep the weeds and grass from invading the garden area. Fill in around the board with soil, keeping the board straight. Tap the board into the soil, using the mallet, to allow the soil to grab onto it. Pack the soil tight around the sides of the board, but not the ends. Fill in gravel for each end if you are not using a closed border.
Repeat the above step with each board. Make sure the boards touch end to end, filling in gravel where any bends occur in the border. This helps with the drainage and keeps the board from rotting. Make sure the boards are tight in the trench, to avoid shifting during freezing and thawing.