The security device of this invention comprises a transparent panel normally locked edgewise upright in the plane of front edges of a pair of vertically spaced shelves of a selfservice rack, blocking forward removal of all but the lowermost one or a predetermined few of a stack of like articles on the...http://www.google.ca/patents/US4682825?utm_source=gb-gplus-sharePatent US4682825 - Security device for point-of-sale display rack and primarily store shelving
