Are you not sure how a cipher key works or even what it is? A cipher key allows you to "unlock" the cipher and decode an encrypted message. If you plan on including a cipher wheel in your escape room it is extremely important you understand how to properly utilize the cipher's key.
Let's take the Union Cipher Wheel for example.
We will use R811 as our cipher key to start encoding our message. It is EXTREMELY important that you use the EXACT same cipher key that you provide your escape room players. If there is any variation on the cipher key used to encode the message and the one used to decode it the message will be completely different. Think of a cipher key as a Rosetta Stone or Babel Fish.
Now that we have our established Cipher Key of R811 we start encoding a message. With the Cipher set to R811 we will encrypt the word CLUE. To do this go to each letter of the word CLUE and see which number is associated with it.
C - 8888
L - 1188
U - 888
E - 8811
So, with a Cipher Key of R811 the word CLUE becomes 8888 1188 888 8811
Hopefully this answers any questions you might have regarding a cipher key, how it works, and why it is so important in escape rooms to use one correctly.