An alternative method for determining the lock-in angle phiL for pinning of the vortices on extended defects has been developed. This method does not require any preassumed criterion for defining phiL. Highly twinned Sm1+xBa2–xCu3O6+y single crystal was used for demonstrating the method. Appropriate scaling of the hysteresis loops measured for different angles between the field and twin planes in highly twinned SmBaCuO single crystal led to a clear discrimination between two vortex dynamics regimes. From this scaling, the lock-in angle was determined to be 6°±0.1° for the single crystal investigated. This method significantly reduces the uncertainty in determining the lock-in angle when compared to all the other currently employed methods.