The end of "Novembeard" reminded me of two things: how much I dislike facial hair and how not all double-edged razor blade packaging is alike. Case in point: The razors I do not like come in a fancy plastic dispensing case that also safely contains the spent blades. The razors I do like come in a cheap cardboard box with no safe way of disposing spent blades. So I did what any maker would do and designed my own disposal box for spent blades.
This Spent Blade Box consists of two tight-fitting pieces. Slide your used razor into the slot and it's safely tucked away where it cannot lacerate the trash bag or fingers. The interior of the box features a little nub that helps prevent razors from sliding out (without a bit of manual and intentional bending action).
OpenSCAD source files are included in the downloads, should you want to tweak the size or fit-tolerance.
Just print the two pieces, inner and outer. Since this is meant to be a solid box, but is also skeletal with its windows and slot, you may want to increase your infill value. Press the inner box into the outer box for a tight friction fit.