1. Take two 40mm blocks and connect them using a shackle.
2. Knot to the starboard cleat on the front crossbar
3. Lead through one of the two 40mm blocks.
4. Lead through the cleat from front to aft.
5. Thread through the port cleat from aft to forward.
6. Through the other 40mm block.
7. And knot the end to the port cleat.