I am looking into get a garden going this year and have been researching ways to be low impact, simple, and productive. A hive of bees is a nice addition. Since members of my family are allergic to bees, mason bees (Which don't sting) are the way for me to go.
I liked a number of the Mason Bee designs available, but as I have said before, the Pacific Northwest causes a few problems for anything out-of-doors. There are a also a few things that Mason bees need that weren't accommodated for in some designs.
The little overhang will keep the openings dryer and protect (to some degree) from birds that will not now be able to attack the hive while standing on top of it, and the small design will allow me to create a few hives and spread them out.
There are holes in the bottom to affix it to the top of a fence post, and on the back to affix it to a south facing wall (In my area).
The drawer design allows me to clean out parasites and remove the larva in late October to store them for the winter. Come next March, I will be able to put the larva out in the sun to hatch. The small lips and grooves are to reduce the ability for any parasite that may get in (And they always do) from getting from one hole to the next. That is a big problem with some home-made hives.
There are two versions of the drawers (Or trays). With and without grips. The drawers fit nice and tight, so if you want the grips, just print that file. No need for both.
As always, I love hearing feedback. Ideas for improvement are always welcome.