Wall mounted holder for an 8mm x-acto knife with a classic fine point blade.
Print the file - You'll probably need to use scaffolding to support the top section, but might want to check the sliced file to ensure you don't end up with a holder full of plastic!
WARNING: Recommend removing the blade from your knife while testing the fit, to avoid nasty finger slices...
You may need to drill the main hole out to 8mm, while squeezing the flexible sides in on to the drillbit.
Attach to the wall using 2 8g speed screws or similar countersunk screws.