Straight Ruler emoji is a picture of a piece of a stationary, used for measuring and technical drawing, in schools in particular (just like the one, represented by 📐 Triangular Ruler emoji). Unsurprisingly, it is used exactly in these meanings — i.e. related to measuring the size of anything, studying in 🏫 School, or drawing certain schemes with different purposes.
Examples of using
“I’ll need to measure it 📏”
“I’ve never used rulers since school days 📏”
How to type