The present invention has: a rod-like main body 11 formed by fitting a plurality of cylindrical rods 111, 112, 113 of different diameters into one another so as to be extendible or contractable to a given length; a sphere-tipped shaft 12 which has a leading end 12a formed in the shape of a sphere having a diameter greater than that of the shaft, and which is provided to one end 113a of the main body 11 in such a manner as to be capable of being folded to a desired angle with respect to the main body 11 and to be capable of retaining that angle; and a pointy-tipped shaft 13 which has a leading end 13a formed in the shape of a circular cone, and which is provided to the other end 113a of the main shaft 11 in such a manner as to be capable of being folded to a desired angle with respect to the main body 11 and to be capable of retaining that angle.
