His collars are as stiff as a board.

他的衣领直挺挺的。

I hung out the washing to dry on a frosty day and when I went to take it in it was as stiff as a board.

在一个霜冻的日子里，我把洗涤物挂到外面晒干，但当我去把它拿进来时，它已硬绷绷了。

Keeping the arm as stiff as a board, swing it in an arc-like motion from the shoulder, making contact in front of the shoulder.

臂要伸直，并保持伸直的姿式不变，以肩为轴把球拍划出弧线，在肩部的前方勾击来球。