a splicing question

[Brian Duff]

I have always used a knot to section off the part of the line I wish to work with while splicing double braid lines, both to provide an anchor point for applying force to bury the splice in the cover, and as a way to keep the relative position of the cover and core during splice working.
Some splice instructions call for this knot , one often sees an overhand loop or a bowline used, however some splice instructions call for one to insert a small fid to 'pin' the relative position of cover to core, and claim this leads to a stronger splice in the end.
My question is that if a fid is used to pin the cover in place, then what does one use to anchor the line while during the core splice back in the cover ? Perhaps someone can describe the technique ?
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...in search of stronger splices,
Brian