I've failed to find a photo of Z's swivel block through which her snubbing line runs.
I know I've also diagrams (from either Larry Pardey or Roger Olson) showing both arrangements: with a simple turning block at the bobstay fitting; and with a swivel block suspended below (or pendant to, if you prefer 18th century English) the cranse iron.
On the latter of those arrangements, I have found one of The Master's (Roger D Olson, former master of BCC Xiphias, Seraffyn, and BCC Nereus, designer of the Cherub dinghy, and a former president of Sam L Morse Co) pedagogic diagrams. See RDO - Anchor snubbing for BCC - 1994.jpg, about 300 K
You'll see that Roger recommended a swivel block at the cranse, a rolling hitch or chain hook at the distal (or outboard) end of the snubbing line, and making the proximal (or inboard) end of the snubbing line around a bitt.
I recommend a snubbing line of 3-strand laid nylon with a length in metres equal to the hull length (about 8.55 metres) and a diameter of that length in millimetres (so about 8.55 mm).That diameter means the line is elastic. And the length means you have enough nylon to absorb shock forces, plus enough to make a cleat hitch.
I recommend making your snubbing line to the midships cleat, not the bitts, with a cleat hitch. That allows you to adjust the length of the snubbing line easily.
That also means that the taut snubbing line is a danger on deck. But it's only on one side.
BCC 116 Zygote,
Scarborough Marina, Moreton Bay, Queensland, Australia
Edited 1 times. Last edit at 12/23/18 08:18PM by Bil.