Purely hypothetical, suppose you need a certain key. This is a key that someone else has in possession, and is amongst a bundle of keys like most people have. How would you go about taking it? But you just need a sneaky way of doing it.
Here's how to make a quick and dirty copy of a key:
1. Get a Styrofoam cup and have it with you when you gain access to the keys. You can even have drink inside of it and be drinking from it...
2. Gain access to the key you need. Note the MAKE and BRAND of the key such as quickset or Schlage lock, etc. This will help later.
3. Press the key against the rim of the styrofoam cup making a good clear imprint into the soft styrofoam rim. This only takes about 2-3 seconds.
4. Keep cup with you but hold it in a manor where the impression of the key is not visible to others, Also don't let your teeth rest against the imprint because this will distort the impression. Try to protect the cup throughout the day making sure you take it home with you at the end of the day...
5. Once you get home take the cup with the imprint and try to find a key blank you already have that matches the imprint on the cup. You have to use skill not to damage the imprint. Many keys are similar, sometimes you will find a key already in your possession that is very close.
6. Once you have a key that matches the brand of the imprint use a dremel tool to slowly and carefully cut the key down to create a matching key from the imprint you made. Once your done, your key should perfectly match the imprint on the cup. If it does, you have yourself a working copy of the key you needed.