Are you talking about a trap or a drop net? I've night fished shrimp off bridges in the intra-costal with drop nets. Pull the wheel apart until you have only the rim (no spokes, rubber, etc. Get some fine netting and make a cone-shaped net that hangs 6"-12" down from it and tie it on with mono. Two lengths of strong cord make a four-point harness to lower and raise the net. We always hung a coleman lantern over the nets to attract the shrimp/prawns and raised the net to grab 'em.