back drawing board
a rectangular board on which paper is placed or mounted for drawing or drafting.
back to the drawing board,
back to the original or an earlier stage of planning or development:
Our plan didn't work out, so it's back to the drawing board.
on the drawing board,
in the planning or design stage:
The shopping center is still on the drawing board.
a smooth flat rectangular board on which paper, canvas, etc, is placed for making drawings
back to the drawing board
return to an earlier stage in an enterprise because a planned undertaking has failed
Collins English Dictionary - Complete & Unabridged 10th Edition
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