Some tips for using concrete curbing forms include using wooden or plywood boards for straight curb forms or pliable plastic boards for curved boards. Use a power saw to cut the boards into shape.
Outline the area where you want to build the curb. Use chalk on pavement of asphalt, but use spray paint for grass or soil. Dig a 2- to 5-inch deep trench about 10 inches wide. Use a hand tamper to compact the soil before you place the boards inside with the smoothest surface facing the inside of the trench.
Place rebar into the trench with 2 to 3 feet of space between them. The rebar holds the form in place and acts as internal support for the concrete. Use a rebar cutter or a circular saw with a diamond cutter to trim the rebar pieces. Mix the concrete and color it, if you desire to do so, before pouring it into the mold. Slowly fill up the trench until the curb is at the desired height.
Smooth the poured concrete with a hand float. Allow the concrete to cure according to the directions on the packaging. Once cured, remove the form, and backfill the curb with soil or gravel.