The vision test involved a black vertical bar centered on a white vertical bar twice the width.

视觉测试包括一个置于白色竖条中间的黑色竖条，白竖条的宽度是黑竖条的两倍。

I'm just doing these two upward vertical bars to show something that is parallel to the surface.

两条平行竖线是平行的符号平行于斜面。

Vertical bars could go either way. A simple little hand thing sort of indicates pull.

唐：垂直条可以向任何方向移动。一个简单的小手表示拉动。

Imagine two blocks of wood lying horizontal to each other, attached to two vertical iron bars.

想象一下， 两块木头相互水平放置， 连接到两根垂直的铁条上。