Update 09/01/2024
These traps have been very well tested and performing nicely for quite a while but it is time for an update.
Over the last couple of years we have encountered a surprisingly large variety of cheese burglers. Ranging from small, incredibly cute and friendly to big, bad and very very angry.
One little dude was soooo cute and friendly he stayed with me for a few days. Most people didn't even notice but occasionally people would approach with a mixture of delight or concern “sorry to disturb but there is a mouse on your shoulder”. To which I generally replied “he doesn't mind being disturbed you are welcome to fuss him”.
After our own experience and some very welcome and useful comments, a number of small updates have been made. The latest one is to include a larger cheese holder which can also be used to aid removal of resident rodent. The cheese hole tapers inwards so soft-ish cheese can be pressed in to fill the space. I also took this opportunity to refine the shape of the latch arm a little bit and to weight the floor some more so that it sits more firmly to hold the door open. You can bash the trap around a lot more without the door dropping.
NOTE The thread section of the new cheese holder is much better printed at 0.2mm layer height. The door, floor and latch pivots also print better at 0.2mm so I just print the whole thing at 0.2mm layer.

Original 2019 text -
We discovered there had been a little visitor under our bath. It seemed to have gone and so we left it. Bad idea!! A few weeks later we were overrun with critters of a mousy nature.
I printed a few varieties of the traps already available and quickly caught a very cute little dude. However, we also had some false triggers and cases of missing cheese but no captive critter. One of the little fellows had the audacity to take the cheese and leave poop in the trap. Another one eat the cheese and then made his own exit hole in the top. I concluded we had some next level critters and we needed to up the game.
The conventional “cage with trap door type” seemed to work the best and so I designed my own version. We seemed to have a lot of critters and so it needed to be easy and quick to make, easy to use, reliable with no missed critters or false triggers, robust and capable of holding the captives for a few hours.
The main box is one piece and quite robust and the trap door is not easy to set off. This means we can pack things back in the cupboard and around or on the trap with no problem.
I made six the first day (using two printers) and that night we firmly re-established who was head of our household (turns out its not me!!).
All we need now is to find a suitable new home for our growing family of very cute little critters. Our neighbours should probably start to worry at this point.
With 0.3mm layer and relatively slow print speeds of 30mm/s a full trap takes 4h3m and can be printed all together on one 200mm bed.
Standard 0.3mm layer settings are OK but 0.2mm layers is better. A part cooling fan is not necessary but as with all PLA prints it will help with quality.
The main body is printed in one piece and so assembly is quite simple (see video):
Print the trap and clean off the boogers.
Fit the tilting floor inside the body by angling it slightly. It will drop into the pivot hole and pivot slot when it is far enough in the body.
Fit the trap door. There is a brace and extra weight lump at the bottom which faces inside.
Snap the door latch in place.
The cheese holder is a simple screw in and the little tang that supports the cheese ends at the bottom when fully screwed in.
Your ready to go get critters.
Warning
The problem with humanely trapping mice is that they are so dam cute you don't know what to do with them afterwards!! If you are like us and have grand kids you may end up buying a cage... and wheel....and little house.....and some tunnels...........