A good helmet is essential. The head is the most-often targeted area on a fighter, and as a result, takes some measure of punishment. The best helmet you can afford is a good safe investment in your fighting future. The local Master of Stables has one and personal copies can be purchased from the Kingdom Stock Clerk . We use the knee line rule.
Any marshal can explain.
We do not corkscrew an opponent on their knees. We turn our opponent out of the sun, when on their knees, and when the flow of the bout permits. Face thrusting is allowed. Local areas also may have certain conventions they use. It is always wise to inquire about local conventions when new to an area.