To clarify there are 2 Sisterlocks tools, the clip tool and the hook tool. The public isn't given access to them. For more details and a photo of each tool, click Kreyola's blog HERE.
In order to gain access to the tool, you have to spend the money to take the class to become a Sisterlocks Consultant. The last time I inquired about the cost, it was around $1000. Before you think that's to expensive, consider some women pay that much to get Sisterlocks.
I prefer my retightenings with the Sisterlocks hook tool because I find it is the best. The clip tool frayed my locks and my initial install consultant and retightening consultant both agree that they get more tension with the hook tool allowing a tighter rotation (meaning no visible holes/gaps in the lock).
However, to each their own. I have seen Sisterlocks maintained nicely with other tools. AND I have seen Sisterlocks maintained poorly with other tools. You should take into account the tool, the retightener's technique and your hair texture.
I hope this helps.