KRuler is a very simple application, with only one aim in life. To measure distances on your screen.
To start KRuler, choose Graphics-> from your K menu.
left mouse button clicking on the KRuler will turn the cursor into a hand icon, and enable you to drag KRuler around the screen.
When you move the mouse over KRuler, your cursor will turn into an elongated arrow, with a circle at one end. As you move the cursor, KRuler will display how far from the point marked 0 the circle on the end of the cursor currently is. KRuler will also display the HTML color code of the color currently under the circle. This is very useful for picking out colours from an image. If you move the mouse far enough that the arrow cursor is no longer touching KRuler, the cursor will revert to normal, allowing you to carry on working with your other applications.
You can change the orientation using the context menu, described in the next chapter.