Through this manual, two different terms are used to refer to the columns in a building. When the term "Column" is used, this refers to a column that spans from one floor to another. When the term "Column Line" is used, this refers to all of the concrete column spans (column stack) that exist at a single plan location. Column lines are delimited by the top and bottom of the structure, by steel columns or by non-column members. Column lines generally span several stories.