I have only seen the sharp pins on the early 720 switches, the ones with the base cut out between the straight and converging tracks - not the newer 720A switches. I have never seen sharp pins on regular track.
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 .