This sheath was mainly for a broken garden shear that got taken apart and converted into a blade.

The sheath consists of 2mm sidewalls with variations in the thickness of the opening, depending on the blade size.
The nub just covers an exposed bolt for safety, or just to reduce the sharpness so that it doesn't damage pockets.

More variants will be likely be added to in the future as I fit more blades.

(Update, 2025-04-21) I particularly like how this design is universal, the 3mm variant fits side cutters as well.

(Update, 2025-04-21) Another advantage of this design is that it can be printed with no supports, which was also intended.

Not a perfect design, but some things I learned from doing it that can be applied to quickly adjust for all manner of blade sheaths in general.

It turns out the opening needs to be slightly less thick than the thickest part of the blade for a proper snug fit.
Also the opening needs to be wider than the blade so that there's wiggle room when putting the blade in, in case things don't completely fit initially.

The garden shear blade measured 2.38mm from it's thickest part and so the initial design used a 3mm thick opening. [1] But it ended up being too loose and came off easily.
That piece ended up fitting a pair of scissors instead.

Then I adjusted down by 1mm for a 2mm thick opening for the 2.38mm thick blade.
It was a bit tight, but enough for the blade to wiggle in, and after a few blade inserts and removals, enough material was trimmed away (likely ~0.38 mm or so) for practical usage where it's not too difficult to move in and out, yet remaining snug.

[1] 3mm is obviously too large now in retrospect and measuring with a caliper, but at the time, I was just quickly eyeballing it with a ruler.

https://www.tinkercad.com/things/9Mip1Uf4zZg-householdgeneric-blade-sheath2025-04-21?sharecode=72uk-ercbVREZzQfk8lXk7DuJ9Z0dxS9ojv75hOatS8