4×5 film holder - Version 3 (including single-sided and double-sided versions)
To address the issue of insufficient film holders, a 3D-printed version of the holder was designed based on the existing ones. It has been tested and found to be usable. 
This model includes: 
Single-sided version of the clip 
2. Double-sided version of the base plate (This base plate is needed to replace the single-sided version when making the double-sided version) 
3. Insertion knife and half-insertion knife (compatible with the plastic 45-piece clamp sold separately) 
Printing Suggestions
1. It is recommended to use matte black PLA for printing. At least the blade part should be printed in black PLA. After trying several brands of black PETG, it was found that they cannot completely block strong light. 
2. For the bottom of the sheet holder, it is recommended to use ordinary support. If you don't want to use support, you can cut the print through the gap, but this requires higher precision from the printer. 
3. After the production is completed, remember to measure the distance between the film and the top surface. According to theory, this distance should be 5mm. 
Accessories
Some black fleece self-adhesive fabric needs to be pasted between the middle layer and the top layer to prevent light leakage. Also, some black strong adhesive is needed to connect the bottom part.

Update Status
2025.02.09: The knife insertion part was updated to make the top of the knife more stable and less prone to breakage.
2025.02.09: The middle plate and panel of the film holder were updated to make film loading easier, and a fleece cloth strip was added to the panel to prevent light leakage.
2025.04.13: The positioning columns and holes were updated to make installation easier.
2025.04.13: The size of the bottom clip was slightly adjusted to make installation easier.
Update Plan
The size and thickness of the photo paper are slightly different from those of the film. A version specifically for photo paper may be designed.
A device for manually locking the knife insertion part will be designed.
A movable label strip will be designed to clearly display the usage of the film holder.
Regarding Copyright
This model can be used for commercial purposes for free, but remember to attribute and provide the model link.