I don't find myself having to do much of this anymore, but back in the day you'd get mandates fairly early on in the game, which caused a lot of bad things to happen.

Noble: I demand that you make me a Platinum coffer for my tomb!

Metalcrafter: Nooooooo! I don't have any platinum yet!

Noble: That's cool, I'll just send you to jail--oh, wait, you don't have a jail yet, because it's early on in the game. I'll just get the sherrif to beat you instead, kay?

*Metalcrafter has been struck down*

Me: WHY DID I EQUIP MY SHERRIF WITH AN AXE?!?!?

So in response, you made 'mandate processors' which involved making a room backed onto the cave river, using a floodgate. Then you'd make a door that you would lock as soon as the dwarf who made the mandate entered the room to pull the mystery lever that you have assigned to him and asked him to pull, so that the room would flood, he would go to his watery grave, and that mandate would be cancelled before my sherrif axed my metalcrafter to death.

And they all lived happily ever after, excepting the fact that replacement nobles tend to arrive pretty quickly and you'd have to make use of the mandate processing room many times a year.