For those who do not know about military rules, you are only allowed to salute with the right hand in the army, and the Airforce. The Navy permits left hand salutes, if you're somehow physically unable to use your right hand. A left hand salute is generally considered to be an insult.
Now I dont know if Ruby is left handed, but I hope hes aware of this when he goes in, or he'll very soon find out
Anyway heres the video.