Align the ruler and the middle of the paper.

与纸张的中部成一条直线。

This is a ruler graduated in both inches and centimetres.

这是一把刻有英寸和厘米的。

Use a rule to measure the width of that cloth.

用量一下那块的宽度。

This ruler has one scale in centimetres and another in inches.

这把上有厘米和英寸二种刻度。