A bed rail having an operating position at one of the sides of a bed and a stored position between a mattress and box spring of the bed. To take down the bed rail, a guard frame portion is disengaged from a base frame portion, then the guard frame portion is pivoted and slid into the base frame portion. To set up the bed rail, the guard frame portion can be slid out of the base frame portion, pivoted relative to the base frame portion, then engaged to the base frame portion and into the operating position at a side of the bed.