Abstract: An elongated generally horizontal support member is provided and a pair of oppositely downwardly and outwardly inclined horizontally spaced apart legs are supported from the opposite ends of the support member with the legs disposed in an upstanding plane containing the support member. The upper ends of the legs and the opposite end portions of the support member include coacting structure mounting the upper ends of the legs from the opposite end portions of the support member for adjustable shifting along the latter while maintaining a predetermined angular relationship between the support member and each of the legs. The coacting structure is also operative to releasably anchor each of the legs in adjusted shifted position relative to the corresponding support member end portion.