The Back Stop tremolo stabilizer was an addition to the Edge tremolo which was introduced by Ibanez in 1987. The combination of the Edge, Back Stop and Top-Lok III nut was marketed as the "Sure Bet Tuning System". It was also referred to as the Block Lock.
The Back Stop has a pair of adjustable springs which push against the tremolo block to help insure that the tremolo returns quickly and accurately to the neutral position. It is installed in the tremolo cavity where it straddles the middle spring.
The benefits of the Back Stop touted by Ibanez include:
- Accurate return to pitch — by compensating for the difference in tension between the guitar strings and the tremolo springs, the Back Stop brings the tremolo back to pitch every time
- Simplified tuning — the Back Stop stabilizes the tremolo so that the guitar can be tuned quickly, with no need to retune
- In-tune string bending — bending a string will not make the other strings go flat, as with conventional tremolo systems. This allows you to hit an open string while bending other notes. Both the bent note and the open string will be in tune
- Tuning stability — the Back Stop locks the tremolo in place so that the guitar remains in tune even if you break a string. This feature is important in live performance, allowing you to finish the performance (or at least the song) without having to retune, restring or switch guitars.
In terms of function, the Back Stop is somewhat similar to the Zero Positioning System (ZPS) featured in the ZR and Edge Zero tremolos although the particular design is significantly different. The ZPS-FX which is used in conjunction with the SynchroniZR is closely related to the Back Stop, but has only a single barrel.
The Back Stop was discontinued in 1989; its disappearance is suspected to be due to a patent infringement claim brought by Kahler. The Back Stop briefly returned in the JEM777 (30th anniversary) reissues in 2017 at which point Kahler's patent had presumably expired.