The X-Chock starts off where the Deluxe Tire Locking Chock left off, but it's new, slimmer design will fit into more axle applications. Fits between tandem tires, it locks wheels by applying force to both tires. Aids in trailer stabilizing and prevents tire shifts. A hand operated plated ratchet wrench (Model 841025, included) turns a drive nut, extending the chocks against the tires for locking and retracting the chucks for removal.