I've been considering for a while what to use. Our chicken run is partially roofed, but not really a big enough area to keep something dry if it rains heavy. We have a small tub that we have been using (until I could find something better), which is under the roof, but against the side of the run and that got wet yesterday. I like the sand box with lid idea, but you may not be home when it rains to cover it to prevent the bath from getting wet, plus I want my chickens to have access to it at all times, even when it is raining. I have also been trying to keep an eye out for a second hand kid's outside play house with roof, as I thought that might work good, but had no luck finding one. We purchased a plastic barrel yesterday (we got it second hand from someone who sells these locally) for a great price. We put it in the run this morning and I have caught one of ours bathing in it so far. It is part way under the roof - I'm keeping my fingers cross it works and stays dry.
