A rung can refer to a level or stage of progress, as in "the bottom rung on the corporate ladder"
. However, the more common meaning of a rung is the horizontal crosspiece that connects the vertical sides or rails of a ladder, serving as the steps or footholds on which you place your feet as you ascend or descend the ladder
. This term is specific to ladder structures and is also used to describe similar horizontal crosspieces or supports in other contexts, such as the rungs of a DNA ladder or the rungs of a chair
