The device comprises a shell (1) which can be fixed on to the steering wheel (2) perpendicular to the plane of the steering wheel. Two spring loaded locking bars are provided inside the shell, which in the extended position (I) are aligned with the steering wheel crown. On placing the shell in position the locking bars tilt under the wheel crown until they reach an end point (II). Each bar has a spring loaded hook (9) which holds the bar in the end position. A hand grip (15) with a lock (17) serves to release the bars and allow the removal of the shell.
