Choose where you want to add pressure-treated wood. Consider edging an existing garden to retain the soil and protect it from wayward grass, or use it to edge a gravel path or driveway to contain the stones.
Measure the width of treated wood with a tape measure. Lay ropes around the garden or surface you plan to edge. The distance between the ropes and the area you're edging should be equal to the width of the treated wood plus 4 inches.
Use a flat shovel to unearth the grass and dirt from the roped-off area. Create a canal 6 inches deep. Pack the dirt down with the back of the shovel to compact the subsoil.
Lay strips of landscape fabric over the bottom and side walls to deter weeds.
Pour 4 inches of crushed rock into the canal and spread it even with the shovel. The rocks improve drainage from the garden or walkway and protect the wood edging from frost heaves.
Measure lengths of treated wood to fit each side of the garden or walkway and cut the wood with a circular or hand saw.
Drill pilot holes through the center of the wood and 6 inches from each end with a 3/8 inch drill.
Place the cut wood on the gravel base against the outer wall so the ends are flush together. Secure the wood to the ground with 9-inch landscape spikes. Drive the spikes through the holes with a hammer.
Backfill the canal with crushed rock to reinforce the wood edging.