straight and narrow

straight-and-narrow的词性：
n.（名词）

1. The way of proper conduct and moral integrity. Often used with the :
正道：品行端一的做人之道，常与the 连用：

kept strictly to the straight and narrow.
严格地按正路做人

straight-and-narrow的词源：

2. [Probably alteration of ] “Strait is the gate, and narrow is the way, which leadeth unto life” (Matthew 7:14)
[可能为] “门是直的，通向生活的路是窄的” （马太福音7：14)的改变形式