Sealing plug closed end

A sealing plug for sealing a hole (11) in a wall (12), sealing plug which can be inserted into the hole through access from only one side thereof, sealing plug which comprises: the plug (13) which can expand radially by accessing thereon from only a first end thereof and a cap seal (24) which covers the other end of the body which can expand and extending body from the same along the exterior of the body length, the sealing cap being of a material which is resistant to the fluid; wherein, when the sealing plug has been inserted into the hole and has been radially expanded so that at least part of the cap adjacent to the hole wall sealing expands and engages the same, the cap sealing it is fixed in the hole with the sealing cap sealing the cap body against access thereto from an opposite end to said first end; characterized in that the sealing plug has an outer rim and therefore can be fully inserted into the hole and installed such that a closed end face (26) of the sealing plug can be substantially flush with a face inside the wall.