This Stanley knife holder, is a 'one print' piece where the blade is placed into the model halfway into the print. After watching numerous 3d printing videos on youtube, I thought I should investigate placing items inside prints. That is what I did.
When printing you start the print and just before it starts printing the layers on-top of the blade, pause the print, place the blade inside and carry on printing. This technique gives you a great finish and allows for a part which requires no assembly whatsoever.
The blade I used for this project was a Stanley Blade, Part No. 11-912 -
Pause the print when it gets to 2.75mm. In Cura, you can do this by going to Extensions -> Post Processing -> Modify G-Code. This gives you the option to pause at a certain height.
This drawing represents the Stanley blade I worked off of in order to get the measurements correct. This drawing was completed by myself.