A tool, for opening a variety of valves associated with gas cylinders, includes an elongated body. One end of the body defines a hook. The body has a generally square cut-out extending through the thickness of the body. The body also includes two or three threaded holes which enable a set of threaded pins to be screwed into the holes. The body also includes an opening defining regions of distinct widths. The tool can be used to remove or insert a cap or cover on a gas cylinder, to operate a valve of a welding gas cylinder, to open or close a nut or fitting associated with a gas cylinder, and to open or close a valve wheel associated with a gas cylinder. The tool thus simplifies the management of gas cylinders, by reducing or eliminating the need for auxiliary tools such as wrenches and hammers.