Concrete forms are typically erected out of plywood and 2-by-4 supports. Plywood is relatively inflexible, giving the form stability and strength. The downside to wood forms is the inflexibility in shape. Wood forms are highly difficult to bend without the aid of expensive, specialised tools. Modern engineering has created plastic and manufactured-wood substitutes that are highly flexible and extremely sturdy. Creating an 8-foot round form requires using a plastic form, available from most building supply retailers, and ground anchors.
Drive a wood stake into the centre of the area that will house the form. Tie a string loosely around the stake.
Measure 4 feet along the string and tie the can of marking paint to the other end. Measure from the stake to the nozzle on the can to validate that it is 4 feet. Hold the string taut and mark the ground in a circle.
Place the start of the plastic form along the line. Drive a ground stake into the ground with a mallet on the outside of the form. Most plastic forms have holes on the exterior edge for the ground stake to fit through for added stability.
Bend the form around the circumference of the marking on the ground. Hammer stakes in at each point on the form where a hole exists. Place a stake every 12 inches if the form does not have holes for the stakes.
Cut the end of form with a hacksaw where it meets the start. Insert a plastic form joint to join the ends. Place a stake on the outside of the joint to hold it steady.