Look at the garden fork handle. You should see a rivet situated above the prongs in the neck of the fork. This rivet attaches the handle to the fork arm. Remove the rivet by tapping it with a hammer. Remove the handle by pulling it away from the arm.
Look at the fork handle. Note the area in which the prongs join together, on the opposite end of where they touch the ground. This is called the shoulder. Measure the distance from the shoulder to the hole in which the rivet was located, called the tang, with a ruler or tape measure.
Insert your new handle into the fork arm. Tap the spaces between the prongs with a hammer to ensure the fork is situated properly.
Drill a hole into the tang in the same spot in which the rivet was located on the previous handle. Use your measurements to assist you in where to drill. Use a bit that is the same size as the rivet.
Insert the rivet into the hole you created. Tap the rivet with a hammer to secure it tightly into place.