Abstract: A tool is described, which is intended for screwing into place a threaded prosthetic part (6). The tool comprises a turning bolt (1) which has an elongated cylindrical core (2) having at one end thereof a head (3) for turning the tool, and having at its opposite end a portion (4) first threads (5) for fitting into threads in the prosthetic part, and is characterized in that the core has second threads (11), on a portion (10) thereof between the ends thereof, said second threads having a pitch direction opposite to the pitch direction fo the first threads, and a sleeve (13) arranged around the core, said sleeve having threads engaging said second threads, whereby the sleeve may be screwed into contact with the prosthetic part (6) locking the tool in the prosthetic part.