Psosets and trellises are generalizations of posets and lattices respectively. In fact, these notions are introduced independently by E. Fried and H. L. Skala. It is well known that a graph can be used to describe a partial order. In this paper, the concepts of modular, weakly distributive and normal trellises are introduced. We have proved that a trellis satisfying sheering property is modular. It is also proved that every strongly connected trellis is nonmodular. It is shown that every separating element of a trellis is modular and every modular element is weakly separating. Well-known result of M.H. Stone namely “Every maximal ideal of a distributive lattice is prime” is generalized to trellises. It is proved that a relatively complemented trellis is a lattice if and only if it is normal.