A turnbuckle device (11) for clamping concrete shell elements (1, 2), having two claws (12, 13), which may be displaced toward one another, and a wedge (18) or the like, the claws (12, 13) having legs (14, 20; 41), the legs (14, 20; 41) having contact surfaces (30, 31; 43) extending in a plane to rest on struts (7, 21; 50) of frames (5, 6) of concrete shell elements (1, 2), the legs (14, 20; 41) having lugs on their free ends (16, 22; 40), which are capable of engaging behind depressions (9, 15) in frames (5, 6) of concrete shell elements (1, 2), is characterized in that an extension (17; 42; 44; 45) is provided on a lug (16; 40) of a leg (14; 41), which extends away from the contact surface (30, 43) at least partially perpendicularly to the plane of the contact surface (30; 43) of the leg (14; 41). The mounting of the turnbuckle device is thus made easier.