I setup a custom object (called Sensitive Documents) with a child-master relationship to the Contact object. I was hoping to control the security of my custom object independent of the parent object (the Contact). When I go to sharing settings though, it shows as "Controlled by Parent", and if I edit the settings, my custom object is not shown (so I can't change it). How do I modify the sharing settings for the custom object?
My use case is that we need to control the security of attachments independent of the parent record they are attached to, and that's not supported by Salesforce (attachment security is inherited by the parent). I found the suggestion to create a custom object and then control the security of that object, but it's not looking like that's possible. Any other suggestions?