Here's what I deploy as a "survey" tube to detect what is out there:
http://www.bee-quick.com/bee_tube.jpg
Nothing more than some 2.5-inch PVC plumbing pipe with a pressure cap
on the end. It holds a dozen tubes, and could be used for small-scale deployment if fitted with two tubes filled with cocoons from last year
and 10 empty tubes.
Rather than going as fancy as Bjorn Bee for actual "production" pollinator
deployment, I use 1-gallon paint cans which one can buy shiny new from
any paint store for about $1.00 each. They hold about 70 tubes with ease,
which would imply using 6 to 8 tubes filled with cocoons from last season.
I get my tubes in bulk from Knox Cellars, and I also get the paper liners
from the same source.
For non-Osmia bees which might require tubes other than 7mm or so wide,
I use bamboo, which is easy to find in a wide range of diameters.
Drilling holes in wood is tedious, and if one uses hardwood, which one
wants to use to get a "clean" hole and wood that will weather well,
the drill bit wear can get expensive. I like the Knox Cellars "system"
very well, as the paper tubes allow one to inspect and disinfect the
cocoons during winter to kill off the parasites.
Osmia are cute little bees - never make any honey for humans, but never
sting either. Difficult to move the tubes out of crops like apples, as the
cocoons are not yet formed, and vibration/jarring can knock the eggs off
their piles of pollen soaked with nectar. Use extreme care if evacuating
your tubes from an orchard before they spray.