Regardless of where one white and one black square are deleted from an ordinary 
chessboard,
the reduced board can always be covered exactly with 31 dominoes
(of dimension 
).
Gomory's Theorem
See also
ChessboardExplore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W. "Gomory's Theorem." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/GomorysTheorem.html