Gutter (philately)
THE SPACE BETWEEN PANES OF POSTAGE STAMPS THAT CREATES CONFIGURATIONS OF "GUTTER PAIRS" OR "GUTTER BLOCKS"
Gutter pair; Gutter block
In philately, a gutter is the space left between postage stamps which allows them to be separated or perforated.Bennett, Russell and Watson, James; Philatelic Terms Illustrated, Stanley Gibbons Publications, London (1978).