Stick and stake nests
Stick nests are most easily made from straight lengths of dry, pithy wood. Elderberry, sumac, and chinaberry are all convenient. Branches or twigs are cut 6-8" long for horizontal stick bundles, a foot or more for stake nests.
In all cases, one end is drilled to a depth of 4-6" using a sharp twist drill. Useful hole diameters range from 3/16" - 7/16" (5-12mm).
Pith fragments should be knocked out of the hole.
For stake nests, a small notch is cut in the side of the branch, and a pilot hole drilled into the pith. This will be used by some small body bee species that prefer to excavate the pith themselves.
Stick nests are bundled together (here with wire) and hung horizontally.
Stake nests are pushed vertically into the ground.
At the end of the nesting season, stick nests bundles and stake nests can be recovered from the field and stored in a shady place at ambient temperatures. They are easily split to reveal any content of nests (there are likely to be wasp nests too, that had been provisioned with paralyzed spiders or insects).
A drilled length of fire wood is another easy alternative to use at home instead of drilled nesting blocks. Use dry wood and drill across the grain to obtain a smooth hole. The blue orchard bee responds well to this sort of nesting substrate. Face the holes southeastward where they will receive morning sun. In subsequent years, drill more holes to minimize re-use of old holes (and any bee diseases that they may contain).