Wooden Training Swords - Bokken and Shinai - More Info
While practicing with a live Katana may seem like a good idea at first, it is also a great way to end one's martial arts career before it even begins. Thus, to keep their students alive long enough to learn a few things, many martial arts use a practice sword instead of a live steel blade.
There are two main types of practice swords. Bokken 木剣 (know as bokutō 木刀 in Japan) are wooden practice swords with similar weight and balance to a steel Katana. They are the primary weapon in Kenjutsu and are also used in other arts such as Kendo. While unable to cut or slash, in the hands of experts, Bokken are still lethal weapons, able to cause injuries similar to a club, and should be treated with proper respect.
Shinai 竹刀 are bamboo practice swords and are much lighter than a Katana. They are typically used in Kendo for sparring. They pose little danger to an opponent, unable to cause more injury than a light bruise, though it is still considered bad etiquette to treat them as a common stick or cane.
Both practice weapons are at their most dangerous when improperly cared for, as they can fail during a match or shatter. Thus, before use they should be properly inspected to make sure that they have no cracks or fractures.