At someone else’s suggestion, I decided to rattle the butt bar while Atty was outside the trailer and give him the opportunity to sniff and see what was making the noise. Notice that at the first rattle at 00:00, Atty has a small reaction. He has no reaction to the second rattle at 00:08. But at 00:17 the butt bar makes a slightly different noise and he reacts to this difference. Can you see what he did? The sound was a lower-pitched “clunk” versus the higher-pitched “clanks” at the beginning. At 00:22 I try to find out what made it make a different sound. I keep experimenting so that Atty can hear all the sounds it makes.