You need a mandrel with hole in it for the horn so that you can spread the tabs while pressing from inside the shell. A 3/8" rod, flat on both ends with the hole large enough for the horn to pass through works.
When you block a person, they can no longer invite you to a private message or post to your profile wall. Replies and comments they make will be collapsed/hidden by default. Finally, you'll never receive email notifications about content they create or likes they designate for your content.
Note: if you proceed, you will no longer be following .