Some Falcon locks come with an interchangeable core. This core, once removed from the lock, can have the pins removed and changed out. What's even more useful, for those locksmiths that don't want to buy special equipment, is that a Falcon interchangeable core can be repinned with common pins from other locks as long as they fit the cylinder. Once you have all your materials ready, all that's left to do is to put the proper pins in the proper order.
Use the removal key to remove the interchangeable core of the lock. Once turned, you can pull the core out of the lock. If you continue to turn the key till the teeth are facing the bottom once the core is removed, the existing pins will come up out of their independent holes in the cylinder.
Remove the existing pins one at a time. Either use tweezers to pull them out of the cylinder, or put your finger over all of the remaining pins except the one you're removing. Turn the cylinder upside down and tape the edge until the pin falls free into your cupped hand. If you intend on reusing the pins, then separate them by length, so you know what pin is of what size.
Turn your key 45 degrees and remove it. Put your new key in; it will slip in easily with no pins in place. Turn it back so that the teeth are facing the area where the pins were removed.
Push the new pins into the holes according to the pattern of your new key's teeth. Once the new pins are pushed in, turn the key back and forth 45 degrees to check for smoothness. Then turn the key to the upward facing position. Replace the interchangeable lock core in the lock. Once it's back in the lock, the new key will work the same way as the old key does.