Measure the area of your lawn where you need the poly tubing for the underground sprinkler system. Write the measurements down on a piece of paper.
Transfer the measurements to polyethylene pipes. Cut the piping to size with a scissors-type pipe cutter.
Join lengths of poly piping with barb fittings and crimp rings. Slip the crimp rings onto the polyethylene tubing. Slide the end of the plastic barb fittings into the end of the poly tubing. Move the crimp rings so they fit on top of both the poly piping and the barb fitting. Use crimp-ring pliers to tighten the crimps and secure the barb fittings and the pipes together.
Connect poly tubing to sprinkler heads with 90-degree fittings that have barbed fittings on one and a female thread on the other end. Connect the tubing to the barb fitting with crimp rings and crimp-ring pliers. Install the sprinkler head per manufacturer directions.