PROBLEM TO BE SOLVED: To provide a method for directly sensing a strike of a fish by biting of the fish with a main line and to provide a supporting tool for determining location points of the observation points (points for sensing the biting of the fish) in three directions and the supporting tool for setting several sites of the observation points in one direction. SOLUTION: A support is provided and hooked swivels are connected to the top and the lower end of the support. The swivel at the top is connected to the main line and the swivel at the lower end is connected to a sinker. Metal wires to be supporting wires having elasticity are fixed to the support and extended. Each supporting wire is passed through a bead, a fluorescent pipe, beads and an ultrathin pipe in this order mentioned and the tip of the supporting wire is formed into a diamond shape and fastened with the ultrathin pipe. The hooked swivel at the top of the support is tied to each snood and passed through the bead, fluorescent pipe, beads and ultrathin pipe through which each supporting line is passed and connected to a metal fixture for fastening a leader. The leader and a fishhook are then tied thereto. The assembling is carried out for the supporting wires. COPYRIGHT: (C)2005,JPO&NCIPI