Isn't this your ruler?
Is that a ruler?
He reminded me not to forget to bring my ruler
I went into a stationer’s to buy a ruler.
A ruler with scales in inches and centimeters.
He reminded me not to forget to bring my ruler.
The ruler cracked and splintered into pieces.
His mannerism was to have a ruler in his hand and swing it to and fro
A device, such as a ruler, tab, or bar, that serves as an indicator or acts to regulate a motion or operation.
a square having a metal ruler set at right angles to another straight piece.