be utilized to connect the rods fig5 is a perspective view of the joint element of the second embodiment of the present invention the joint element 5 which is made of polysilicon rods connects the rod 1 and the rod 2 by engaging the grooves thereof in the second embodiment the extruding portion of the engaged region is smaller fig6 illustrates the joint portions of the charging material of the third embodiment of the present invention fig7 is a perspective view of the joint element alternate extruding portions are formed at ends of the rods 1 and 2 thus forming linear grooves 1b and 2b when the extruding portions of the rods contact the polysilicon joint element 6 of fig7 can be engaged to the grooves 1b and 2b thereby connecting the rods fig8 illustrates the joint portions of the charging material of the fourth embodiment of the present invention alternate mesa regions 1c and 2c are formed at ends of the rods 1 and 2 when the mesa regions 1c and 2c make face to face contact the joint element 7 can hold the mesa regions 1c and 2c to connect the rods the joint element 7 is similar to that shown in fig7 fig9 illustrates the joint portions of the charging material of the fifth embodiment of the present invention alternate extruding portions are formed at ends of the rods 1 and 2 pinholes 1d and 2d are formed in the extruding portions of the rods 1 and 2 respectively when the extruding.