properly prepared rice straw dried in the shade for 3 days. This is formed into a target with bamboo running through. The straw represents the flesh and muscle. The bamboo represents the bone. Targets are on stands. All standard cuts can be practiced this way. Sometime a whole kata would be performed on a series of targets set out in sequence .
Myth of the left handed Samurai
All swords men where right-handed traditionally in Japan this was due to the samuraiís protective energy ki or inscription placed by the sword smith on the right hand side of the tang. In order to be protected the ki needs to point toward you. This meant it had to be on your left hip for a right hand draw. This ki would protect your from evil and bad spirits. So if the sword is slung for a left-handed fighter he is unprotected from evil
I will give you another reason not normally considered. The samurai fought on foot in ranks cutting simultaneous into their enemyís ranks. Can you imagine the disorganisation of such an attack and the many opening for counter attack that would be created by a mix of different cutting position and angleís!
Thirdly the code of BUDO prohibited sword drawing, painting, calligraphy poetry writing and archery with the left hand