Measuring stuff or drawing a straight line.
a ruler is used to measure inches or 1 foot
A ruler.
measuring scale, tape, or ruler is used.
Jim used his ruler to measure the length of his finger. Bob is the ruler of the world.
Ruler
The answer depends on the graduations marked on the ruler.
the ruler was used to measure the length of my book.
Plastic is generally used as an insulator. A plastic ruler would not be a conductor of electricity.
A ruler is used to help us measure things.
Measuring things
Ruler
a ruler