This Butterfly Roost is designed so that you can put sugar water or honey water onto the sponge, which attract the butterflies. The slot represents a crack in bark that the butterflies would naturally roost or hibernate in, once they crawl in there is a branch fastened in there that has rough bark, and they can climb on to it and roost over night some species will hibernate.
This one is made from a bowl. Maximum dimensions mounted reclaimed pine with larch top is Length 20cm, Width 19cm, Depth 18cm