Use a tape measure and permanent marker to locate and mark a single drill hole on the side of the handles of two stall forks. Mark the holes three inches above the upper surface of the steel frame of the forks.
Mount a marked fork in a steel vise. Drill a 1/2-inch hole through the handle at the mark on its side. Repeat this process on the other fork.
Stand the two forks up and facing each other with their tines touching.
Slide a 1/2-inch by 4 1/2-inch machine bolt through both holes in the two forks, connecting them together. Wrench the bolt tight and test the movement of the two forks, when moved back and forth, to verify there is tight movement. Place a lock washer onto the bolt end, and place and tighten another nut against the lock washer.
Weld the nuts and washer together to form a permanent lock and prevent it from loosening.