I used to use safety pins and needles and thumb tacks, soda tabs, that's more scratching tho
I really liked bikini razors…
Exactos of course (I stole the blades from the art department of my school lol), a box cutter or a retractable knife, and it's easy to take the screws out of a pencil sharpener, broken glass could work. In a psych ward a girl taught me how to cut myself with bra wire.
As others said, sanitize whatever you're using… big deal