Joint issue – when two or more countries issue stamps on the same date to commemorate the same event or honor the same person, place or idea. Usually the central vignette is the same, framed with different lettering and denominations.
Joint lines – lines that appear on gutters between sheets in rotary press printing and are caused by ink filling the space where the edges of the curved plates meet when mounted on the press cylinder.
Journal tax stamp – a stamp denoting taxes on newspapers but often conferring free transmission through the post.
Jubilee lines – dashes of color surrounding certain sheets or panes of stamps that are added to prevent damage or excessive wear by the pressure of the inking roller to the printing plate. These lines first appeared on British stamps of 1887, Queen Victoria’s Golden Jubilee Year. It is called the ‘co-extensive’ line when broken, and it is called the ‘continuous line’ when unbroken.