The steering lock should make the steering of the vehicle wheels impossible without a key, a chip card or anything similar. Apart from this, modern locking systems also make it very difficult to override them.
Earlier it was simpler for car thieves. Even when the vehicle was properly locked, they could succeed, using a lot of force, in shearing off the cotter-pin and thus making the vehicle (not always interference-free) steerable. Now the gear rim for the cotter-pin is no longer connected directly with the steering wheel. Between them there is a corrugated tube pressed in which, over a certain (very high) torque, provides for slip between the steering and the gear rim. This torque is too high for reasonably exact steering of the vehicle, and too low to shear off the cotter-pin. 09/09