rubber cushion

Because socket type spark plug wrenches sometimes break the porcelain around the plug as they are slipped on or off, cut a short piece of rubber hose to fit snugly inside the wrench. Forced into the tool so that it clears the lower shank that grips the base ofthe plug, the rubber hose within the hollow tool acts as a cushion to protect the plug's porcelain insulator from accidental breakage.