Bearing in mind a cat got into one of my boxes with a double internal passage with a brick in to make it shallower, I don’t know why I was surprised a fox cub managed!!
I would leave some water outside too, in case, if you haven’t anyway for birds, etc. I find here, that certain hogs don’t go in the boxes and especially with the dry weather as much water around outside the better. I have water places both ends of the garden and a tiny pond. Not a large garden, but I don’t think you can leave too much water out, and 24 hours a day, in case. I use mostly plant saucers outside about 10 inches/25 cm. wide or more, some near to cover so if a hog is out in the daytime it wouldn’t need to go far out of cover to get a drink.
