  The ground state properties of a frustrated spin-1/2 system is studied on a
trellis ladder which is composed of two zigzag ladders interacting through rung
interactions. The presence of rung interaction between the zigzag ladders
induces a non-magnetic ground state, although, each of zigzag ladders has
ferromagnetic order in weak antiferromagnetic leg interaction limit. The rung
interaction also generates rung dimers and opens spin gap which increases
rapidly with rung interaction strength. The correlation between spins decreases
exponentially with the distance between them.
