It is very hard to rotate the ruler!
There should be a button in order to rotate the ruler.
Mr Yaswanth commented
Yeah, I tried to move or rotate I get confused and left using it
Personally, I think the ruler is pretty awkward and should be replaced by an easy way to draw a straight line which can be easily sized and rotated. Pulling up a giant and somewhat clumsy tool to draw a line seems pretty non-optimal.