Unanswered Tips for making boxes that can fit together

I'm trying to use the printer to make boxes that would hopefully be able to get opened with a bit of friction. Making them is a bit tougher than I anticipated - does anyone have tips for making or sizing the boxes so they more or less snap together?

Thanks!

*attached is an example of a box I tried to make - they don't fit together though I would like to change that.

 

Are you making the model or is it one that you downloaded?

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These are models that I'm trying to make for personal use.

 

What program are you using

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Currently using the program I've sunk the most time into using - Blender.

 

You want to create two parts that have a tight tolerance. Tight enough that it holds the parts together, not so tight they cannot fit. I use about 0.2mm tolerance for parts that I want to tightly lock about 0.3mm for hinges, etc.