My potters wasp houses work!!!
As I was finishing this house a wasp started filling it. Caterpillars and then a single egg before sealing it up and making another chamber.
These busy little wasps like smaller holes around 5mm. They will build in larger holes but if you are targeting Potters wasps I have found this size is the best.
You can use bamboo or drill holes in wood. I usually put them in a dry place or provide a good roof to keep it dry. If the houses are small you can bring them into a dry shed over winter. If they get damp pupae can rot.
