A ruler is a very common thing

By the looks of it, I’m long and slender and dressed in flowers, and what a beautiful dress! The blue sky is covered with clouds that look like cotton
Underneath the clouds there is a meadow where the grass is standing up like a little soldier, looking vibrant and alive.
sandwiched between them were white flowers. I am 20cm wide and 20cm long, with five small vertical lines sandwiched between these numbers. That’s me – the ruler.
I am very good at what I do. In maths class, when my little master couldn’t draw a straight line, he took me out of the stationery bag to help him.
If the owner takes the pen and aligns it to the length she wants to draw, the line comes out straight.
I am not only beautiful, but I am also very good at what I do.