Two questions on Stalag 17

first, every visit by the postman/messenger caused exitement among the inmates. whenever the crowd got too noisy, he would shout “at ease!” and the inmate animal would reply “at ease!” i don’t get it.

second, of what material was joey’s flute made? it must have been wood since animal was whitthling a replacement to the one thrown into the mud but why the shape?

It’s not a flute – it’s an Ocarina . It’s usually made of clay, but all sorts of materials have been used:

Animal was one of the barracks clowns – his repeating “at ease” was him actng up. It had no official function. He was poking fun at the straitlaced “nerdy” official.
The authors of the original play were inmates in such a camp (whch was not the Stalag Luft III of The Great Escape and The Wooden Horse). The situations were based in large part on their own experiences. But the play was extensively rewritten (in part by the director, Billy Wilder) for the film.

thanks. (why oh why am i so slow at combating my own ignorance?)