Enter your combination while packing. Have your three or four-digit code line up with the marks on the body of the lock before pulling the shackle upward. Codes run left to right or top to bottom, depending on the model.
Make sure your combination code is correct so the lock will open. Gently turn each dial, making sure it is completely in position.
Spray some penetrating oil into the lock. Rust or ground-in dirt stops the mechanism from working properly. Work a little of the product into the dials and shackle. Spin the dials around a few times and re-enter your code if the lock has not been working properly.