Try this for practice only!
DISCLAIMER: This is for instructional purposes only. All LEO should abide by their agencies policies concerning Use of Force.
Try these, its really basic. Important: I recommend that your other hand grabs the subjects hands or wrist immediately after the block to prevent them from using the backend of the weapon to attack you.
You must step out to the side so that your attacker can not continue to repent their attack!
FYI: In a knife fight, you should always mentally and physical prepare yourself to get cut.