Gutter (philately)
the space between panes of postage stamps that creates configurations of "gutter pairs" or "gutter blocks" / From Wikipedia, the free encyclopedia
Gutter in philately (stamp collecting) is a space between printed stamps. Gutters may separate sheet of stamps in panes. They may, or may not, have some printing. The gutter between the stamps is often the same size as the postage stamp.[1]
There are other related philatelic terms: