The National Self-Harm Network publishes a guide called Cutting the Risk: Self-Harm, Self-Care and Risk Reduction. The guide covers anatomy, including the locations of major veins and arteries and different types of tissue, including the consequences of cutting through each type. It’s not sensationalistic about this, but rather very matter-of-fact. Other topics include wound care, infection prevention, ways to manage bleeding, caring for burns, and advice on when to seek medical help. The guide recommends first aid supplies to have on hand.
The National Self-Harm Network also has a Harm Yourself Less Workbook that is written by people who self-harm. It asks a lot of reflective questions to help people explore all aspects of their self-harming experience. This can be used as a personal learning and growth tool, or it can be worked on with a therapist to enhance the impact.