The lavatory contains a long trough for which the knights can use for urination. Crude toilets are also included for defecation. The design is all stone walls with candles, and no privacy walls.
Lavoratory, Inside Castle
king
guard
I am a guard at the royal castle.  I am brave and strong.  It is my duty to protect the king.
I shall protect your life good King as you use the lavatory!  You may defecate in peace knowing that I guard your royal rump! Don't be absurd!  I have my own private lavatory.  Defecation is not the reason i have followed you here.  I have a job for you. Oh . . . well, that is disappointing.  What task have you for me? I need to you to seduce my wife, the Queen. Well . . . are you sure you wouldn't rather have me guard you while you visit the privy? Why must everyone test my patience! Are you denying my request?  No my liege!  You have my sword, and I shall do anything you command! There are rumors that you are the most popular guard with the tavern wenches. Well, I don't like to brag, but . . . Perfect!  I have my suspicions that my queen may have a wondering eye.... Hmmmm, what do you need me to do exactly? I will have you appointed to her personal guard.  You will follow her day and night.... and report back to me.