The ends typically have metal or plastic hooks to help attach the cord to the anchor points. The stretching part of the cord enables the tightening around the object being secured using the cord. The moment you stretch the cord, it retracts with an opposing force. Whichever one you are going to use, it is good practice to check that the bungee is fit for that purpose. If it is too short, it will not reach. If it is too long, it will not hold the item tightly enough. Before using it, even check it. Check for frayed material, broken strands, or severe stretching in hobbling areas.