This is a test of commonsense. Complete the next sentence:

How to copy a key
Hold the teeth on one side of the key over an open flame until they are charred.
Use a lighter or a lit candle. Move the teeth of the key back and forth over the flame.
It should take around 1 or 2 minutes to blacken one side of the key. Once the key is charred on one side, set it down until it is cool to the touch.