Abstract: A removable, expansion sealing plug has an annular seal formed of an elastic material, which seal is expanded by a fruste-conical expansion member when the expansion member is drawn into a retention member, the retention member having an outer surface with screw threads, and the expansion member being rotationally fixed, but axially movable, relative to the retention member. When installed, retention member screw threads fix the plug in position and prevent forcible expulsion from the installation hole and the expansion of the seal causes compression of the seal between the wall of the installation hole and the expansion member and frictional interference between the seal and the installation hole and between the seal and the expansion member, thereby preventing the rotation of the plug within the installation hole.