A project we're working on has
place objects with attributes like name, address, phone number, and URL. Users can view a place and click to call, map, or browse their site.
In our project, one and only one place can be set as the "default" place, meaning that its fields are used as the fallback for all empty fields of non-default places. So if a user clicks to call the Sales department, but they don't have a number listed, it will call the default place (Reception, for example) instead.
A content manager creates the places using a set of web forms, but the problem we're running into is how to label the "default place" field in a way which clearly communicates that this will take the "defaultness" from the old default place.
How do we communicate that there can only be one default place?
Related, we're debating whether it should be a checkbox that can be checked while editing a place ("default" as an attribute) or a button the manager clicks while viewing a place ("make default" as an action).
Do you choose a default place by checkbox or button?