a unit of <#stamp=stamps>, sold by the post office, comprising one or more <#bp=booklet panes>. Traditional booklets used cardboard covers stapled or glued together to protect the enclosed booklet panes. With a few exceptions, traditional booklet panes used water-activated gum. Contemporary booklets (both <#convbooklet=convertible booklets> and <#vendbooklet=vending booklets>) contain self-adhesive stamps and are sold as single panes. Contemporary booklets do not have separate covers. The backing paper serves as the cover.