Dropdowns are a great way to prevent from breaking your rig. The dropdown allows you to bring the banger and/or nail and dome down and away from the rig itself. That way, when heating the banger or nail you don't get the rig hot. When the glass is heated/ cooled the material actually expands and contracts which makes the rig shatter and crack over time. The dropdown acts as a buffer between the rig and the heated nail or banger. This way if anything breaks from the heat, it will only break the dropdown and not your expensive rig.