Tactical decomposable regular group divisible designs and their threshold schemes

Some methods of decomposing \(v(=mn)\times b\) incidence matrix of regular group divisible (RGD) designs into square submatrices of order \(m\) are described. Such designs are known as tactical decomposable designs. As a by--product, resolvable solutions of some RGD designs are obtained. A relationship between tactical decomposable designs and \(\left(2,\ n\right)-\)threshold schemes is also given.