Since we cannot be certain that a knife MAY be involved..all techniques should be trained as though a weapon is being used. A prime example is kote gaeshe where often you shall see the aikidoka making large circular movement and turning the wrist in a large circle. Attempting spinning movement against a knife shall get you cut. Swinging the knife hand up high shall bring the knife close to the eyes/throat. Therefor this manner of executing kote gaeshe is WRONG. Below the proper triangular entry against a knife and empty hand attack. The principles of triangular entry off line along the line of attack are constant. Proper understanding of aikido as a self defence art should eliminate many of the rather involved techniques often taught. Also the instant it is realised that a weapon is involved ara waza (severe technique) must be used.facing a knife is incredibly dangerous. Attempting to control a knife attack is suicide.