Packing is the process of placing padding over or around the genitalia in order to create the appearance, when clothed, that a penis, or breasts, are present. Packing is often done as part of a person's gender expression, and some may desire bottom surgery in order to create a biological neophallus. Packing can be done using any available material, but prosthetics specially designed for the process can be bought. Some penile packing devices may also include mechanisms designed to allow the wearer to urinate while standing.