Toothless was patient while Duo examined the fin. It was a common occurrence that someone would ask Hiccup how the fin worked or how he made it, and he'd call the dragon over to explain.

At least with the old one, it was common. This new one, well... he hadn't had it long enough to really gain that much attention. When Duo was done, Toothless flexed his fin and pulled the entire tail around.

He half moaned, half roared ever so slightly and jutted his nose towards the rim of the walls. Did Duo know what was up there?