Before installing concrete edging you will need to plan your garden perimeter first. Unlike plastic or metal edging, you will need to work with sharp 90-degree corners. Once you measure your area, purchase the amount of block you will need from a home improvement center. You may need to adjust your measurements if you do not want to cut concrete block. Work with the sales clerk in determining just how much concrete block you will need for the project.
With a spade shovel, dig a trench around the perimeter of the area where you're installing the concrete lawn edging. Dig the trench deep enough so you will have 1 inch to 2 inches of the edging above ground level after you place the ¾ gravel in the bottom of the trench. Make the trench wide enough for the thickness of the concrete block you are using.
Pour an even 1-inch layer of ¾ gravel into the trench (¾ gravel is gravel that is no larger than ¾-inches). This gravel will help keep the concrete block from settling out of shape and maintain a clean, even appearance.
Drive 2-foot wooden stakes into each corner if the trench about 1 foot down. Measure from the ground level up 2 inches and tie a string to one of the stakes. Run the string to the next stake in line and measure from the ground up 2 inches and tie the string to the second stake. This will give you the line where you want the top of your blocks to be when you set them in the trench. Repeat this measuring and tying of string until the perimeter of the border has a string wall.
Set the corner blocks into all the corners first. The top of the block should meet the string. If you need to raise the block, add gravel.
Place the straight blocks into the trench, butting each end of the blocks together. Add gravel where necessary to ensure that the tops of the block are even with the string.
Fill the trench with the soil you dug out and tamp the soil down with a board. Remove the stakes and the string.