Abstract: A gate locking system for securely locking a rolling type gate in a closed position within an opposing pair of U-shaped channel guide rails. The guide rails include aligned apertures formed through opposing front and rear walls. The gate also includes an aperture which is aligned with the guide rail apertures when the gate is in the closed position. A guard plate is positioned exteriorly of the guide rails and also includes an aligned aperture. An elongated member of a lock is inserted through the various apertures to lock the members together in the closed position. The head of the lock is retained exteriorly of the guard plate while the distal end of the lock extends beyond the rear wall of the guide rail. A securing member cooperates with an extended end of the elongated lock member to retain the lock in a clamped position between the opposing walls of the guide rail so that the closed gate is captured therebetween. The securing member is under the operative control of a rotatable portion of the lock.