To solve a difficult work in an important procedure to make a capsized bottom hook block ball by forming a parallelogram link of a contact piece which comes into contact with the conical section of a slide being loosely fitted on a central shaft, a supporting piece which is axially supported by a columnar section pedestal, and supporting arms, and providing a groove applying blade on the upper section.

On a strut 2 which is erected on a base plate 1, a slide 3 of which the upper section is a conical section 4, and of which the lower section is a columnar section 5 is loosely fitted on, and the slide 3 is vertically moved by a protuberance 6 on the columnar section 5 by a lever provided on the base plate. Then, a parallelogram link is formed of a contact piece 13 of which one end is brought into contact with the conical section 4, a supporting piece 10 of a pedestal 9 provided on the upper end of the strut 2, and a pair of supporting arms 11, and on the upper ends of the supporting arms 11, a groove applying blade 12 having a blade tip which is not sharp, in the vertical direction, is axially supported. In addition, a coil spring 14 is attached in the vicinity of the lower end located on the outside supporting arm 11, and in-between the supporting arms 11, in such a manner that the whole body may become annular, and by this constitution, the application of a plurality of grooves toward the center on a spherical body section can be easily performed.