Ratchet tensioner

The turnbuckle has a pipe (1) comprising counter-rotating inner threads emanating from both pipe ends, and a ratchet unit (4) for rotation of the pipe. Threaded spindles (2, 3) are screwed into the threads, where one of the spindles has a groove (2.2) running in an axial direction. An arresting element i.e. locking bolt (11), is adjustable in a radial direction and insertable into the groove. A sliding sleeve (5) is displaceable in an axial direction along the pipe and provided for insertion of the arresting element into the groove.