Line Tool: Click and drag to draw a line of any length and in any direction. If you hold down the shift key while you draw, you confine the direction of the line to either the horizontal, vertical, or an angle 45 degress with respect to either polar direction.

In the line's Properties Box, you can change its color (black is default); add an arrow and determine the arrow's size and location; make the line dashed and select the size of the dash step; and lock the position of the line.

Placing a line on top of another object connects the line to that object.