You have multiple options:

1. Just don't have a type column. All STI magic will be disabled automatically.
2. If you have a type column but want to use it for something else (WAT?), you can set self.inheritance_column = :_non_existing_column in the class definition
3. (Untested) In the parent class, set self.abstract_class = true

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This technique is useful to implement form models / presenters, where you want all the goodness of ActiveRecord but want to add additional logic for a particular screen (e.g. class SignUp < User).