These gutters are the zones along which stamp sheets are normally cut to produce the panes. In some cases, however, postal agencies will sell unsevered sheets of blocks that cut across one or more gutters. This example is termed a traffic-light gutter block because it also contains color blocks in the gutter area that are used to check the alignment of the multiple print colors. The block shows two intersecting gutters, one vertical and one horizontal. Note that different stamps can be printed in separate panes of the same sheet.
Essays differ in some details, large or small, from the final printed stamp.
In this example, this stamp was never produced and it is termed an unaccepted essay. The example above shows a set of trial-color proofs. See article on essays, proofs and special printings for more details. Unlike the Azerbaijani privately-printed example given above, most do not carry a denomination. The example above notes the official opening of the Troll oil field in the Norwegian sector of the North Sea.