Abstract: A locking device used to lock a trailer towing mirror to a vehicle is disclosed. The trailer towing mirror is of the type which is mounted between the seam bisecting the hood and fender of the vehicle and the edge of the wheel well of a fender of the vehicle and has a plurality of supports which connect to the vehicle and which connect to each other and are fixed in relationship with respect to one another by at least one turnbuckle. The locking device includes an elongated member having a first end and a second end and is formed of a material substantially resistant to sundering. In the first end of the member is a first hole of sufficient dimension to fit over one of the supports and in the second end of the member is a second hole of sufficient dimension to allow a shank of a lock to pass through the second hole.