Norco Deluxe Model 28005 - 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 (included) turns a drive nut, extending the chocks against the tires for locking and retracting the chucks removal. Requires 2 1/2"  clearance between tires. Opens to 10".