More about Lincoln, and it's relevant to the conversation . Lincoln is a lovely cat with one truly unsavoury habit. Fortunately it's only happened a couple of times so far, but he has taken giant poops in front of the door right under the mail slot. We don't know whether or not he has ever actually used the litter box (three cats, all with outdoor access - hard to determine), but he really needs to learn to use it. Does anyone have any good tips on training a full grown adult cat to use the box?