Abstract: A tool is provided for repairing valve elements in pressurized systems having a valve stem and a valve core. A block member has a passage therethrough at which a valve stem engagement structure is affixed. A slide member is dovetailed to slide along the block member. The slide member also has a passage therethrough such that in one sliding position of the slide member relative to the block member the respective passages align to allow a tool to be passed through the slide member, block member, and valve stem engagement structure to service the valve. When the passages are misaligned, the passage through the block member is substantially sealed from gas leakage by abutment with the dovetail-attached slide member.