This is a little tool for the pivot screw of Enlan jack-knives (folders).
Enlan is using a triangle screw for the pivot joint e.g. on the Enlan EL-01... knife. To adjust the knife's folding mechanism you need to buy a special tool.
Do not buy it - just print it. :)
Depending on your print material you may need to scale the object a little bit to match the screw. Try a setting of 99% or 101% if your first print does not fit on the screw.
UPDATE:
I just uploaded a version for older knives that have a screw with a silghtly larger tri-wing shaped head.