Lock Rings are installed between the Top Sub and the Bowl, and are designed to keep the Top Sub from inadvertently unscrewing from the Bowl. Lock Rings are typically used when a significant amount of torque is being applied through the overshot to the fish (such as encountered during back-off operations). The Lock Rings can be used with either a Basket Grapple or a Spiral Grapple, If a Spiral Grapple and a Type A Packer are being used, then a Spacer Ring must be used in conjunction with the Lock Rings. The Spacer Ring is installed into the Bowl and on top of the Type A Packer. When the Top Sub/Lock Ring assembly is installed into the Overshot Bowl, the Spacer Ring will secure the Type A Packer in the Bowl.