It's a soft, rectangular object that is part of a bed.

这是一个柔软的矩形物体，是床的一部分。

The standard method for rounding corners is to use an arc of a circle to connect the perpendicular sides of a rectangular object, which produces a somewhat abrupt transition from straight to curve.

圆角的标准方法是用一个圆弧来连接矩形物体的垂直边，这产生了一个从直线到曲线的突然过渡。