Postage stamp separation

The Penny Black is imperforate.
Separation of imperforate stamps by scissors, knife or tearing often leads to uneven margins on the stamp as in this 1853 stamp of Van Diemen's Land.
Vertical pair of 1d red, from Plate 70, perforated with the Archer experimental roulette
Perforated and imperforate versions of the same Austrian stamp of 1920
A rouletted United States revenue stamp of 1898
"Bantam" stamps from South West Africa showing normal and rouletted perforations. Three stamps could be printed using the paper normally used for one. Produced during World War II as an economy measure.
This pair of coil stamps clearly shows the pattern of perforation holes; also, on the left side of the pair, the stamp was torn, while on the right the perforations were cut with scissors or knife.

For postage stamps, separation is the means by which individual stamps are made easily detachable from each other.

Methods of separation include:

  1. perforation: cutting rows and columns of small holes
  2. rouletting: small horizontal and vertical cuts
  3. diecutting: cut paper to shape using a metal die—used for self-adhesive stamps.