Arthur has spent a week or so in the small box of his choice. The first one had sides that were unaccountably floppy after he slept in it for just one day. The second one, though about the same size, was found to have a more sturdy constitution. Having spent all this time sleeping in the second small box, Arthur feels that he must have trained himself down sufficiently to tackle the last of the small boxes. This one is a tricky customer: it is not actually much smaller than the other boxes, but it has high sides and a very solid constitution. The high sides largely preventing spillage, so it means that all of Arthur must be folded skilfully into it. But, as mentioned, he has been in training, and he is small enough now.
The second picture shows how important it is to first establish that abluting can be done in a place of residence before commencing to sleep there.