The general

rule of thumb is to find the center of balance of an object, and
understand how it flies. For example, a screwdriver can be
treated like a knife. If the handle is heavier, throw the object
by the blade, using full rotations. If the blade is heavier,
throw it by the handle, using half rotations. Practice with
such irregular items on large cardboard boxes. It will be
surprising just how many “household” items can be trans-
formed into deadly throwing weapons in the hands of a
Ninja who has mastered the art of throwing. But be careful;
items not designed to be thrown may be damaged or ruined
by such practice and training. It is often enough just to know
that the principles of Ninja knife throwing can be applied to
other objects as well.