In a die which has a regular polyhedron form and which can be opened into a continuous
polygonal form on a plane, boundary areas (Rb) between planes (11 through
16) on the inner side of the regular polyhedron have inclination angles
determined according to the regular polyhedron. In addition, engaging portions
(21a, 21b, 24a, 24b, 25a,
25b, 26a, 26b) not exceeding the
respective boundary areas (Rb) are placed on the boundary areas (Rb) of predetermined
planes (11 through 16). Such a die is formed by injecting plastic
resin within a mold (31, 32) according to the form of the opened die. This
realizes a three-dimensional die capable of being opened onto a two-dimensional
plane, which has only been fictionally conceived, and further provides a manufacturing
method thereof.
