For people with lots of old safety razor blades lying around. The nut screws on over the top piece, to hold the blade on. The cap clips over the blade.

(The longer versions are good for cleaning aquariums.)

UPDATE 12/2020: Added a new cap design that's easier to use. Slightly reinforced the base of handle screw. Added 7.5" length handle. Adjusted shortest handle design to allow using new cap.

Dimensions:
Length: 3.875 inches (short), 5.25 inches (regular), 7.5 inches (long), 9.75 inches (very long)
Width: 2 inches

Creality CR-10

No

20%

Used a 0.4mm nozzle with 0.16mm layers.
If not printing with the old cap, it might help to print the handle alongside a taller object, to give layers of the screw time to cool.
I also suggest using solid infill for areas less than 70mm^2. (This reinforces the screw.) In Cura, the setting is "Minimum Infill Area".