What does this mean?
"Sensei has no hands; no pockets" is an expression of respect and gratitude for your sensei. It means that while your sensei is in your company, they don't carry anything for themselves or pay for anything themselves. (Although Robert Mustard Sensei will often insist
on buying rounds and who's going to argue with him?).
It also means that the uchi deshi (or senior students) accept any challenges on sensei's behalf if the occasion arises. Sensei cleans up if you lose, though.
You also need to know how to fold a hakama if you're following this tradition properly.