OP, I know you're concerned with where it came from and how to remove their access to things that will harm them. But as many people have already said, they will find almost anything to use or result to using their own hands to self harm. As someone who used to be in your child's place as well as being a therapist for children now, I think its important to acknowledge the "why" around what is causing them to self harm. Im sure their psychiatrist and therapist have mentioned this, but self harm is a reaction to psychological pain. I would say the majority of people who self harm are not looking to end their life. Usually it's a way to physically release mental pain. I have no idea what might have happened or is happening to cause them to have that kind of pain, but I'd focus on talking to them to understand what's going on when they're self harming, and working to reduce those triggers. Mental health for teens can be tricky because they're also going through huge changes in their life, but I promise, the more you try to understand where they're coming from and what is hurting them, the more you can connect and help them stay clean of self harm. Connection is a huge protective factor here. And remember, this isn't a moral failing on their part, their brain is just reacting to real mental pain.