Abstract: An adjustable width barricade includes a frameless, flexible, washable, aesthetically attractive, and generally-rectangular barrier that mounts between banisters of a stairwell. The adjustable width barricade does not require drilling into the stairwell banisters and is removeably mountable without damaging either the structural integrity or decorative finish of wooden banisters, balusters, rails, or posts. Multiple strap-like fasteners attach the barrier to stairway banisters or posts, including posts having vertically varying diameters and configurations, that are non-parallel relative to each other, that are non-perpendicular relative to the flooring surface, or that are otherwise asymmetrical. A plurality of rigid, structural support members are inserted into vertical channels in the barrier that maintain the height of the barrier when installed.