drawing board

noun2

1. •
   A plane surface or table to which paper can be fastened for drawing purposes.

   • The T square, used by architects, makes very good parallels, if made to slide along the smooth edge of a drawing board, or a straightedge laid and kept steady on the paper. — 1815
2. •
   (figurative) The planning stage of a project.

   • At the time we doubted that such a locomotive would be given swift consideration—at least in detail; but the evidence suggests that one is already on the drawing board and will appear next year. — 1962