Hanging your banners with bungee cords is the preferred method when installing your banners outdoors. With the potential of winds that can possible tear your banners if no flexibility is provided, bungee cords stretch and will give in windy conditions prior to the tension of the wind tearing your banners. Using less flexible methods to hang your banners can result in your banners having a sail effect and when something has to give, your banners tear as a result.
Bungee cords can also be effective for hanging banners indoors, because of the flex properties bungees possess. By securing your banners even inside a building your banners will continually be more taught than if they are installed with rope. If the knots in your rope give a little, your banner's presentation will sag, whereas bungees can continuously provide tension making your presentation look more professional.