Where Is It?
The constraint block is found in the Primary drawer of the Blawx toolbox.
What Does It Do?
The constraint block is used to set out a combination of statements that cannot all be true at the same time.
The constraint block is an outer block. It accepts a single stack of statements, which is valid if it includes at least one statement.
A constraint is used to express a set of facts that cannot all be true at the same time in any of the models returned by any question block.
For example, you might use a constraint block to indicate that a person cannot be both the testator of a will and the trustee named in the will at the same time.
Using the constraint block can cause your code to run more slowly.