Tested a few versions of this one, and I found that I was missing a more distinct place to put my thumb. :-) As a design study I designed this knife in Fusion 360 with inspration from other designs and a handle more fitting my own hands with place for thumb and fingerguard close to the actual edge. The fingerguard is sufficient for keeping your fingers off the edge, while the thumb grooves makes it easier to add some pressure while cutting and gives better control.

This knife uses regular Stanley trapezoid shaped razor blades, with 3 optional magnets allowing it to lock closed or open. If nuts/screws are adequately tightened, the magnets are really not needed, but it is an option you can select, and in my opinion only needed to keep the knife closed in a pocket. When in open position you hands hold over the hinges / links, keeping in safe in an open position.

You need:

• 2x: Link Hex Nut
• 2x: Link Countersunk
• 1x: Blade Handle (or alternative handle with finger guard)
• 1x: Blade Holder with thumb grooves

Non Printed Parts

• 4x: M3x16mm Button Head Screws
• 4x: M3 Nylon Insert Nuts (Locknuts)
• 2x: M3x5 Button Head Screws
• 2x: M3 Nut

Optional and really not required:

• 3x: 6mm OD x 3mm Magnets

I have tested this one now over time and it has more than sufficient strength and stiffness for safe use, and feels great in the hand. When you find the sweetspot for the correct tightness of the screws/nuts, it is easy to open and close, while still not opening unintentionally. I have printed these using the Creality Hyper PLA, and I highly recommend this. Strong and easy to use.

Updated. Some minor adjustments done. Alternative handle with fingerguard to make safer to use.