But the angel said to them, "Do not be afraid. I bring you good news of great joy that will be for all the people. Today in the town of David a Savior has been born to you; he is Christ the Lord. This will be a sign to you: You will find a baby wrapped in cloths and lying in a manger." - Luke 2:10-12
The cross is to remind us of our Savior's dying for our sins and the nail remind us of the terrible price He paid. Our creations remind us that it was His Love that held Him on the cross... Not the nails.