since we're talking about "rope" stuff, I have been intrigued by these rope shackles and how to build them.

I have not seen one used at the bitter end of a line (say, to replace a shackle for a spin sheet to the spin clew). Is this able to be done, or do you have to build the rope shackle and then create an eye splice on the bitter end of the working line (spin sheet, etc).?