Pens are marked by a triangular green pennant that flies on a tall pole over the pen.
In Nivet Territory, Pen operators are not supposed to breed Gens on their own -- or their taxes will go way up. Slina tried branching out into breeding Gens.
Gens are caught in the Wild or allocated to a Pen from a Genfarm. The Pen System is seen as the government's method of distributing Gens equitably across the Territory, and Gen distribution is the government's main reason for existing. Junct Territory government began as a 'settled in band of Freeband Raiders' but becomes a bureaucracy with real power because of the Gen Tax system.