The Top-Lok III is a type of locking nut designed by Ibanez and installed on some Ibanez guitars.
A locking nut is one component in a double locking tremolo design. The locking nut effectively locks the string at the nut while the string is also locked at the bridge. This design allows the guitar to maintain tune when the tremolo is used by reducing the length of the string which is stretched.
The drawback of the locking nut is that the nut 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 III has three individual pressure pads, each of which locks down two adjacent strings. The screws on these pressure pads are adjusted using a 3mm hex wrench.
The Top-Lok III is paired with a string retainer bar which sits behind the nut. The purpose of the string retainer is to increase the string break angle at the nut. This ensures a consistent break angle for all of the strings and helps to keep tuning consistent when the pads are locked down.
The initial version of the Top-Lok III was secured with two screws running through the back of the neck. This design created a weak point on the neck which was prone to cracking. Starting around 2003 a redesigned nut was secured from the top, eliminating the holes running all the way through the neck.
Differences from other Ibanez locking nuts
The Top-Lok III differs from its predecessors the Top-Lok and Top-Lok II mechanisms by integrating the function of the nut with the string locking mechanism. Previous versions sat behind a traditional nut. The advantage of the integrated design is that it eliminates the friction and wear caused by the string sliding through the nut slot.
The Barless Top-Lok which is typically paired with the Edge Zero tremolo is a similar design which, as its name implies, forgoes the use of the string retainer bar on the headstock. This design requires a steeper break angle on the headstock.
Note that the pressure pads in these diagrams are oriented incorrectly. They should be rotated 90 degrees so that the ridge of the pad is parallel to the strings.
- Edge tremolo which contains a user manual for the Edge and Top-Lok III