If you drop something on your decking like a hammer it is going to mark the wood. One of our customers has told us that tne thing you can do to get rid of the dent is to cover the wood with a wet cloth and hold a warm iron on the dent. You will be amazed at how the the dent disappears when the warm moisture swells the fibres of the wood. Be careful not to have the iron too hot or your decking will suddenly look worse than before.