PURPOSE: A paraffin wax melting in a specific temperature range is added to a tackifier containing more than 50wt% synthetic rubber to increase thixotropic property of the tackifier, prevent the sagging and improve the adhesion.

CONSTITUTION: A tackifier composed of more than 50wt% of synthetic rubber such as isoprene or butyl rubber, when necessary, an oil of naphthenic hydrocarbon, a plasticizer of, e.g., dioctyl phthalate, a tackifier of, e.g., rosin-modified xylene resin, a filler of, e.g., calcimum carbonate, colorants, perfumes, is combined with 0.1W 10wt%, on the basis of the total weight, of a paraffin wax melting at 37W75°C. The resultant mixture is heated up to a temperature higher than the melting point of the paraffin wax added and stirred to produce the objective tackifier. The tackifier is coated on sheets of paper, aluminum foil or plastics and used as a sheet for rat- capturing device.