Shuriken refers to a blade hidden in the hand, but it is usually used to mean a Japanese thrown weapon. Shurikens can be divided into two subvarieties: bō shuriken (棒手裏剣) i.e. needle-like blades designed to be thrown; and hira shuriken (平手裏剣) which are metal disks or throwing stars. Both are employed in Bujinkan. Most frequently, business cards or other safe substitutes are used in place of throwing stars in training, while metal bō shuriken are thrown at a target board. Japanese bō shuriken are thrown so that there is as little rotation as possible so that the blade points at the target as much as possible during its flight towards the opponent. Two main methods of throwing exist: jiki da-ho in which the blade does not revolve; and han-ten da-ho in which the blade spins like in traditional western knife throwing. Throwing techniques are challenging and require plenty of practice. Bujinkan practitioners are given instruction in shuriken throwing from various positions and distances. In addition to the bō shuriken, Bujinkan makes use of the square-shaped Teppan and Senban varieties of hira shuriken. Shuriken are also used as makeshift mêlée weapons in close combat. Many traditional samurai styles include the shuriken, and were therefore not an exclusive ninja weapon. In all probability, shuriken jutsu developed from throwing stones and sharpened coins.