Use the string level to make sure the string is horizontal. Use measuring tape to find the distance between the string and ground (Image 1). Dig out the base of the pathway to the depth of your bricks plus an additional two inches for the crushed stone base layer (Image 2). This measurement will guide you as you excavate the ground with a shovel to establish a consistent, level surface.
Use the claw of your hammer to dig a trench for a metal pipe on each side of the walkway (Image 1). The pipes serve as guide rails to create a consistent 2" deep crushed stone base layer. Lay the pipes in the trench (Image 2). Use the string level and measuring tape to keep the top of the pipe exactly two inches above ground level and beneath the crushed stone base layer.