Final answer:
To enforce rules on every object of a certain kind, a constraint block should be defined in object-oriented programming, ensuring that all instances abide by the specified constraints.
Step-by-step explanation:
To apply a constraint to every object of a certain kind, you should define a constraint block. In object-oriented programming, a constraint block specifies a set of restrictions or rules that must be adhered to by all instances of a particular class. For example, if you're designing a class for a bank account, you might want to ensure that the account balance never goes negative. By placing the relevant constraints within a constraint block, you ensure that this rule is enforced for every bank account object that is created from the class.