I think this is supposed to be used to set up #25 chain, not actually tension it actively. It is supposed to make closing a loop of chain easier basically. (don't take my word for it)
Or I'm wrong, and you leave it in for a quick tension option. Just don't get it caught in the sprockets.
The guy to ask is Chief Delphi user
ajlapp, he is affiliated with 221 Robotics Systems and could answer your questions.
Link to user profile:
http://www.chiefdelphi.com/forums/member.php?u=385