Okay so first off, although I have called this a lock it is not a lock, but more a latch. I origin ally designed it for a treasure chest project I made a few years ago. The chest was made from cardboard and so the lock was made specifically for cardboard. When I decided to upload it, I wanted it to be more versatile, so redesigned it to fit anything. More like a traditional lock. The current design requires a couple of springs, I used ones I got from amazon. Unfortunately, these are no longer available, but I have put the link her for reference on the size. https://www.amazon.co.uk/gp/product/B01EOIEM7U/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 I will eventually try printing some springs and rivets if you wanted to attach it to cardboard as I did, some check back in a week or so for any updates.