Restraints can of course be used to provide search limits to any of the parameters used to describe circular failure surfaces, including the more traditional abstract points in space used to define a circle centre. Restraints can also be used in a similar way to provide search limits for non-circular failure surfaces, and truly provide you with control over search areas.
As well as providing search ranges Restraints allows you to define the number of trial surfaces to be generated and analysed within each of those ranges. The actual number of trial surfaces is up to you; GALENA can generate and analyse up to around 1 billion trial surfaces for each analysis, although it would be extremely rare to even attempt such numbers.
The norm would be to follow a sequential 'fine-tuning' approach with around 3,000 - 5,000 trial surfaces for an analysis, followed by further analyses using the critical failure surface as a seed.
So, as you can see, Restraints provides you with a very powerful mechanism, that gives you real control in the real world.