Use the ruler in the drawing tab in PPT 2019

Starting with PPT 2019 you can use a ruler to draw.

Go to the Draw tab (if you do not see it, activate it by going to File - Options - Customize ribbon - check the Draw checkbox in the list of tabs.

Click the ruler button.

The ruler appears.

You can move the ruler by dragging it with your mouse.

To rotate the ruler put your mouse pointer on it and use the scroll wheel of your mouse. With every turn of the mouse wheel there is a 1 degree rotation. If you turn the scroll wheel upwards you rotate counter clockwise, if you turn the scroll wheel downwards you rotate clockwise.

You can also manipulate the ruler using your keyboard. Press Shift+F6 to be able to move the ruler. Pay attention to the dark grey line that appears as a border.

To move it use the four arrows on your keyboard.

To rotate the ruler with 15 degree steps, press Alt+right arrow (clockwise) or left (counter clockwise). For 1 degree steps use the Alt+Ctrl+ left or right arrow.

Beware that the Alt+Ctrl+left arrow or right is also used to rotate the screen from horizontal to vertical in Windows 10. You can undo this using the Alt+Ctrl+ up arrow.

See the following video demonstrating the possibilities.

You can use the ruler to draw straight or angled lines. Or you can use it to align objects on your slide. See the following videos.