Abstract: An explosive plug for blocking tubes comprises a tubular metal body closed at one end by a solid head and having at the other end a surface-contact region containing at least two spaced apart charges actuable by a detonator. The metal body when placed in a tube to be blocked is so arranged that the surface-contact region is coaxial with but at a distance from the tube so that successive explosion of the charges causes the surface-contact region to be radially spattered against the interior of the tube thus producing a reliable metal weld or welds extending along a substantial part of the end region of the tube.