• Click on point A.
• Click on point B to draw the line.

• Click on point C.
• To draw at an angle, press Shift.
• When point D is clicked, the line is drawn.

• Use them to position the cursor on point C.
• Press Enter
• Use them to move to point D.
• When Enter is pressed, the line is drawn.

More Info

• When drawing with the mouse, lines are adjusted to plumb or level unless Shift is pressed.

• When drawing with the keyboard, the keys in the number pad move a fixed distance.
  This distance can be adjusted with the Plus and Minus keys.
  The separate arrow keys always move one pixel on each click.

• A line can also be drawn by dragging between two points. When the button is released at the end point, the line is drawn.