The bamboo tubes should be at least 6" in length. For some reason, (
Nature...
.) if the tubes are not long enough, then only males will be hatched. The males come out first, scout the neighborhood, and then perch at the bee house, waiting to mate the newly hatched females!! (Seriously, they "stalk" the house. Go and YouTube search "Mason bees mating" and you don't even have to watch any, just look at the options you're given, you'll see - it happens right on the bee house.)
I saw a video of one male, crawling in and out of all the tubes, checking to see if anyone was awake yet!!
I know it's a little late, but if you build another, put a little more overhang on the "roof" or give them an awning...to keep out rain. Or maybe hang them under an eave on the shed or garage...
Hang it somewhere it will get morning sun.
They only forage about a hundred yards
*, so if you want them to use your house, put it fairly close to a pollen source. The female makes a little ball of pollen and nectar, then lays an egg on top of it. She then collects mud to build a partition wall, and the process starts again. You'll need a little mud patch nearby, too!
* One website said 300 yards, so I figure better safe than sorry.
Hang it outside in the spring, overwinter in shed or garage. (This will also help it last, since you are not going to treat it with anything.
.)
If you really want a new hobby, watch this video.
@BigC, you have enough hobbies, maybe it's best you
not watch it!!