More information on working with rulers can be found here.

Apart from simply dragging its endpoints, you can either click the ruler or one of its endpoints to manipulate it.

Ruler point

The ruler point tab:

The ruler point does not have a popup menu.

x	The x coordinate of this point (left to right).
y	The y coordinate of this point (top to bottom).
Move point	Move only this endpoint of the ruler.
Move ruler	Move the whole ruler.

Ruler

When the ruler is selected, the following tab appears:

When the ruler is right-clicked, the following menu appears:

Delete	Delete the ruler.
Glue	Glue the ruler to avoid accidentally moving it.
Rotate...	Rotate the ruler.
Flip	Mirror the ruler.
Layer	Move the ruler to another layer.
Horizontal	Position the ruler horizontally. Click again to put it upside down.
Vertical	Position the ruler vertically. Click again to put it the other way around.
Length	Set the length of the ruler.
Scale	The scale of the ruler. The displayed length is relative to the modeling scale.
Change style	Change the way the ruler looks.
Font	Set the font of the ruler text.
Size	Set the font size of the ruler text.

Page url: https://www.anyrail.com/help_en/index.html?rulers_tab.htm