Wrap a sheet of newspaper around the pipe and align the overlapping edges. Make a mark in chalk along the edge of the newspaper. Remove the paper and use the chalk line to guide your cut.
Lay the pipe in front of you on the ground. Place the cutter on the ground with the pressure screw facing up and the chain fully extended.
Open the chain jaws by turning the pressure screw counterclockwise until it stops.
Wrap the chain around the terra cotta pipe, matching it up with the chalk line you marked, and attach the closest link to the upper jaw. The chain will wrap around the pipe from underneath. Make sure the excess chain comes "out of the top of the hooks and into the clear," as Reed Pipe Tools recommends.
Turn the pressure screw clockwise to close the jaws tightly around the pipe. This will mark the pipe along your chalk line.
Increase pressure. Different models have different pressure mechanisms. If your model has a ratchet mechanism, increase pressure with the ratchet until the pipe breaks. If your model has two arms, tighten the pressure screw until you have marked the pipe around the circumference, then step down on the handle to make the cut.