Bats usually roost in cracks and crevices in trees and buildings, but need more help than ever before as the number of old trees declines and modern building methods make buildings less accessible to them. They also need help by re-establishing an environment that encourages the kinds of insects that they feed on.
We use untreated reclaimed timber for our bat boxes, as bats are very sensitive to the kind of chemicals used to preserve wood. We usually have at least one batbox in stock, but can make more to order, but if you like making stuff yourself, here's how to build a bat box from The Wildlife Trusts website.
If you are planning on putting up a bat box check out making, siting and maintaining bat boxes first.There's lots of information about bats and bat conservation at the Bat Conservation Trust website and a delightful PDF, Stars of the Night produced by Wild About Gardens, which will appeal to children and adults alike.