Except in the most casual dining establishments, they are usually provided as a matched set, sometimes distinguishable only by the number of holes on the top of the shaker. Designs range from small, plain glass screw cap containers (invented by John Landis Mason, inventor of the Mason jar) to more ornate works of art. Sometimes the design refers to some pair of related objects—such as a replica of a West Highland White Terrier containing salt and a Scottish Terrier containing pepper. Designs may also relate to specific occasions or holidays. As a result of this diversity of design, collecting salt and pepper shakers is a hobby. Design of salt and pepper shakers has also been used to transmit cultural perspectives about race and other cultural values.