Abstract: In certain embodiments of the invention, devices for locking a spring assembly on a tandem-axle vehicle are provided. Some embodiments relate to methods of locking a spring assembly on a tandem-axle vehicle. In some embodiments, devices for locking a spring assembly on a tandem-axle vehicle, such devices comprising: a block having a top surface, a bottom surface, and a plurality of side surfaces between the top surface and the bottom surface, wherein the top surface may or may not be parallel to the bottom surface, wherein the distance between the top surface and the bottom surface is between about 2 and about 25 cm, and wherein the top surface is angled between 5 and 45 degrees with respect to the bottom surface; wherein the block is adapted to be inserted between a first leaf spring and a frame of a vehicle to lock the vehicle's spring assembly.