This chapter discusses what parameters must be considered in the design of columns, some preliminary sizing tools, and how to do the in-depth calculations. Columns make open space possible. Without them, we would be subject to the limitations of walls. Columns range from round poles to rectangular sawn sections to structural composite lumber of a variety of shapes, sizes, and layups. Buckling is the driving consideration in column design. Slenderness is the driving parameter for column buckling. Taller or thinner columns are more susceptible to buckling. Because of this, the most efficient timber columns are square–providing the same buckling capacity about each axis. To gain a conceptual understanding of column buckling, take a straw and apply a compression load at the top. In fact, buckling is the driving consideration in column design. Slenderness is the driving parameter for column buckling.