stiff as a board

stiff as a board

Also, stiff as a poker. Inflexible, rigidly formal, unbending, as in This cloth is stiff as a board; what happened to it? or There he stood, stiff as a poker, unwilling to give an inch. The board in the first simile for rigidity is a slab of wood; the second, alluding to the iron implement used to push around logs in open fires, dates from the late 1700s.
See also: board, stiff
References in classic literature ?
Both Summerlee and Challenger were limping heavily, while I still dragged my feet from weakness after the shock of the morning, and my neck was as stiff as a board from the murderous grip that held it.
But he found the hide had dried as stiff as a board, and as he knew naught of tanning, he was forced to abandon his cherished plan.