A pickle fork is a heavy steel wedge with a two-pronged fork at the end. It is designed to separate tapered joints in steering and suspension systems, such as ball joints and tie rod ends. These joints use a tapered steel stud that fits tightly into a matching tapered hole. Over time, the joint wedges itself so tightly that it resists coming loose even after the locking nut is removed.
To use the tool, you slide the prongs of the fork between the joint housing and the steering knuckle. Driving the end of the handle with a heavy hammer forces the wedge deeper, pushing the two parts apart until they snap free. Because the wedge action applies heavy pressure against the rubber dust boot, using a pickle fork almost always tears the boot. This makes it a destructive tool, best used when you plan to discard and replace the joint anyway.