  The notion of a supercharacter theory was proposed by P. Diaconis and I.M.
Isaacs in 2008.
  A supercharacter theory for a given finite group is a pair of the system of
certain complex characters and the partition of group into classes that have
properties similar to the system of irreducible characters and the partition
into conjugacy classes. In the present paper, we consider the group obtained by
the Borel contraction from the general linear group over a finite field. For
this group, we construct the supercharacter theory. In terms of rook
placements, we classify supercharacters and superclasses, calculate values of
supercharacters on superclasses
