well I had the same problem - I used the same set of "tools" every time I self harmed. My T asked if it was ok for her to take them away and have them disposed of. After a LOT of negotiations, me saying no, I backed down and let her. It was good to get rid of them, it was cleansing somehow.
But unfortunately it didn't stop me, I just went out and bought more of the same "tools". And before that, starting using other things. It's hard though, I felt guilty for my T because she tried so hard to make a positive change.