You can use the Thalia Capo from either the bass or treble side of your guitars neck.  Check out this short video demonstration to see it in action.
The vast majority of users have no problem squeezing the Thalia Capo.  However, some may find it difficult to apply with one hand.  The following video shows how to easily apply the capo to the neck with 2 hands, at which point you should be able to move it around with just one.