This one caused me to scratch my head a little back in the 90s. First you need to retrieve the lock from the fuel tower area. This is done by picking it first (for another achievement) and then picking it up off the ground. You also need the meat from Todd's fridge in his trailer.
At the salvage yard, secure the gate by using the lock on it. Then use your hands to climb the chain. You will now be inside the yard. Move down to the lower area and head right. You can enter another area with cars. Use the meat on the nearest car. The dog will jump in the car. Then back out of the area. In the main salvage yard, move your cursor up towards the actual magnet/crane towards the upper right. Your cursor will turn to an arrow allowing you to enter the crane controls. From there, switch to the controls to lower the magnet down. Then turn the magnet on. Once the car is attached, raise the magnet. Then leave the control booth. You are now free to grab the forks from the lit pile in the main salvage yard.