Splicing on deck

[Tedder]

So far, all my double-braid splicing has been at my bench, but now I need to work on deck with the fittings in place (travelers, down-haul, out-haul)--it is too much trouble to remove them. At the bench, I can hold a shackle or eye and bring the splice home pulling against a loop securely fastened, but in this case, the shackle is securely fastened while the rope is free (except for a loop tied to keep the core from wandering).
What is the theory to proceed in this case? I am sure you riggers do splices in this condition all the time, so what is the technique?
Thanks!

[Brion Toss]

Hi,
Oh, and you have touched on a matter of High Art. It is true that splicing in the field -- even in motion in the field -- takes you to a whole other level, if only because the orientation and tools you have become accustomed to are no longer available. But first, it it probably not too much trouble to remove those fittings, because the alternative is probably more trouble than you can imagine. So disassemble the traveler car and end controls as needed, messenger that halyard down if needed, do what you can to approximate shop conditions. Ideally the biggest difference will be that in the shop it is difficult to drop your tools in the water.
If you really have to splice to a fixed point, straighten any corners before entering the tool. It can take some yacht yoga. Tension the loop knot, and maintain that tension as you run the splice home. Tricky to find an anchor, sometimes, that leads fair to the fitting. But really, just disassemble.
Fair leads,
Brion Toss