A locking device is provided and operable to retain an article intended for display and handling in a designated area. In particular, the locking device is formed with an adjustable fastening loop, which can assume an extended position to receive a free end or a portion of the article, and a retracted position to secure the article in the fastening loop. The fastening loop can be adjusted between the extended position and the retracted position, so that the locking device is adapted to receive and secure articles of various sizes. The locking device is preferably mounted to a fixture, such as a display table or counter via a tether cable. When the cable is mounted to the fixture, the locking device is capable of retaining an article in the designated area and preventing the article from being removed from the designated area. For example, the locking device can secure a sample item to a designated area, such as a display counter in a retail store.