Coast-Knives is using a screw with a 5-point head for the pivot joint. To adjust the knife's folding mechanism you need a special tool. For the tool you need five steel rods Ø1.2mm x 4mm. 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.