Envelope for a bed having side rails

An envelope sized and adapted for use with a bed having a mattress support and one or more substantially horizontal side rails vertically spaced from the upper plane of a mattress when placed on a mattress support, comprising an enveloping portion and a flap, the enveloping portion having inner and outer sheets closed along their corresponding respective top and side edge portions, said enveloping portion having an opening defined by the bottom edges of said inner and outer sheets, and said flap extending freely from a bottom edge portion of one of said sheets, said enveloping portion being adapted to fit over and envelop one or more of the vertically spaced side rails, and the flap being adapted to extend under the adjacent longitudinal lower side edge of a mattress and having means for securing the flap to a mattress support in a manner that prevents a mattress placed on a mattress support from shifting out of its proper position thereon, and prevents a bed occupant or his or her appendage from becoming lodged between two side rails and/or between the lowermost of the one or more vertically spaced side rails and a mattress or mattress support.