This is a holder to be attached to the empty HSW inserts, to insert the often used round hygrometers.
With the slots in the back and the offset from the wall there is no problem in reading temperature and humidity. The hygrometer slides easily enough in and can be removed for battery changes. In theory it can still be used standing on the flat bottom surface as well.
How to print:
My HSW style of choice: Polymaker Polyterra PLA Marble White
The base model I've used is reneeceldesigns Temp / Humidity Holder - Circle, of which he posted the stp file on makerworld (go check it out, the model is awesome!)
→ https://makerworld.com/en/models/102038#profileId-108677
The author marked this model as their own original creation.