Inflatable rats, or union rats, are commonly used in the United States of America by protesting or striking trade unions against their employers or against nonunion contractors, serving as a sign of opposition and to call public attention to companies employing nonunion labor. Unions have been using them for years against companies that employ nonunion labor, and employers have filed lawsuits charging that the use of the giant inflatable rats constituted unlawful picketing, and some courts have agreed. Though in May 2011, the National Labor Relations Board (NLRB) held that union use of an inflatable monster rat is not considered an unlawful activity when directed at a secondary employer. Also, in 2011 National Labor Relations Board (NLRB) in Sheet Metal Workers Local 15, 356 NLRB No. 162 (2011) ruled that the inflatable rat did not constitute a signal picket, but instead, constituted symbolic speech which is not subject to secondary boycott rules. This holding allows the union not only to place the inflatable rats at neutral entrances, but also to place them at locations where the picketed company is absent. The practice of using inflatable rats in union protests may have something to do with the usage of the word "rat" to refer to nonunion contractors.
While the inflatable rat sometimes varies in appearance and size, it generally features large teeth and grotesque features. Many unions have nicknamed the inflatable rat "Scabby the Rat", a reference to scabs.