[McBruce]

Law 86
C. Substitute Board
The Director shall not exercise his Law 6 authority to order one board redealt when the final result of a match without that board could be known to a contestant. Instead, he awards an adjusted score.

A multi-team contest has several sets of preduplicated boards; players begin with two boards and get successive boards from a central table until they have played all of the boards in the set. At the end of a round before a long break, after teams have met to compare, boards 9 and 10 in one set are found to have been misduplicated. There is time to add one or two substitute boards at each table to allow all teams to have played the same number of boards, instead of awarding both sides average-plus and slightly inflating the VP economy. But Law 86C seems to make a perhaps-needless distinction between one, and more than one, redeal:

--a team which has played different versions of ONE board clearly cannot add a substitute board into a match once the score with one to go is known, since Law 86C clearly prohibits this.
--a team which has played different versions of TWO boards could make the argument that the wording of Law 86C does not prohibit TWO redeals, even though the score with all but two boards compared is known.

I dubiously suppose a TD could decide that the Introduction's final sentence "unless the context clearly dictates otherwise, the singular includes the plural" applies here. But how far do you go? If there is a major accident in the preduplicating room and there are many misboards, are we going to have a bunch of matches scored as 14-10, 17-6, 12-12, on a 20 VP scale because some teams chose a specific colour?

[VixTD]

In this case "one board" really does mean "one board" and not "one or more boards".

You may think there's not much difference between playing a single board and playing two boards when the outcome of the match is otherwise known, but that's where the line has been drawn. The EBU TD guide (the White Book) has the following comment on this law:

Quote

There is no difficulty in this Law with replaying a board played in an earlier stanza, or if two or more boards need to be replayed.

[RMB1]

The result of the match cannot be known if there is a subsequent (scheduled) stanza (between the same teams) in which the substitute board(s) can be played.

The "do not replay a single board" law only applies if the board is to played in a one-board stanza at the end of the match.