A 'shinai' is a Japanese sword typically made of bamboo used for practice and competition in 'kendo' (modern Japanese martial art). The shinai was developed in an effort to reduce the number of practitioners being seriously injured during practice.

Due to its lighter weight a 'shinai' can be wielded in a fashion that allows quicker strikes than would be practicable with a heavier sword. This also makes shinai popular in producing movies and television shows; a prop shinai with a thin metal covering can look similar to a metal sword, while allowing cinematic, showy strikes that are nevertheless fairly safe to perform.

A 'shinai' must be properly taken care of or it can pose a danger to both the user and the people around it. When not in use, 'shinai' used in 'kendo' practice should be either laid on the floor or leaned vertically against a wall. When a 'shinai' is placed on the floor, it is considered poor etiquette to step over it.

The ancestor of the modern kendo shinai is the 'fukuro-shinai'. This is a length of bamboo, split multiple times on one end, and covered by a leather sleeve.

More Info: en.wikipedia.org