The Top Lok is a type of string locking mechanism designed for Ibanez and installed on some Ibanez guitars.
The Top Lok is used to lock the string behind the nut. This design allows the guitar to maintain tune when the tremolo is used by reducing the length of the string which is stretched. The chief drawback of a string locking mechanism is that it must be loosened with an hex wrench if the player needs to tune beyond the range of the fine tuners on the bridge.
The Top Lok was used with the Pro Rock'r tremolo and a graphite nut, which it sits immediately behind on the headstock, creating a Double locking tremolo system. It features three locking pads which are clamped down by tightening a hex bolt. Each pad locks two adjacent strings. The center pad is set back from the outer two pads to allow access to adjust the neck truss rod.
The Top Lok II is a similar design with the three pads aligned in a single plane. The Top Lok II was suited for angled headstock designs. Both of these behind-the-nut designs were supplanted by the Top Lok III, which was introduced in 1986 along with the Edge tremolo. The Top Lok III integrates the function of the nut with the string locking mechanism, thus eliminating the friction and wear caused by the string sliding through the nut slot.
- Nut (string instrument), Wikipedia (English), archived April 2016.