The spanner tool is a metal device having a shape similar to a winding key. It can be used to loosen the siphon head screw and to remove the valve needle. Old-style spanner tools have a hole in the middle, but the function of it is unknown to me.

Without having a spanner tool, the siphon head screw can be loosened with the blunt side of a knife and the valve needle can be removed with a large Phillips head screwdriver.