How does the kicking strap secure to the boom and how is it tensioned?
On the original boat (i.e. as supplied in the '60s and '70s) the kicking strap was a simple piece of line with a loop in one end. The loop went over the boom and there was a wooden block on the top of the boom which held the loop. The other end just went to an eye on the middle of the stowage bulkhead (that's the one just behind the aft mast step) and was secured by a knot.
Improving the kicking strap by adding blocks and a cleat was common. For a long time the class rules limited kicking strap purchase to 2:1. A typical set up of this type has the kicking strap starting on the stowage bulkhead or the becket of a block on the attached to the stowage bulkhead. Then it runs up to a block attached to the boom then back to a block on the stowage bulkhead and then to a cleat. A combined single block with "V" jamming cleat and becket was often used in this system (i.e. SeaSure 0013). Others fitted a jamb cleat under the thwart (seat) on a angled block or on the side of the daggerboard case. There are so many possible arrangements that it's a case of looking at your boat and trying to work it out. Bear in mind that part of the system may have been robbed for something else!
These days up to 8:1 purchase is permitted and is common on racing boats often using a cascade of blocks and with the kicking strap lead to cleats each side of the thwart so it can easily be adjusted by crew or helm when hiked out.