The crayon tool is used for freehand drawing of lines one pixel wide.
To use the crayon, position the cursor on the Canvas and press the mouse button. Drag the mouse to draw, and release the mouse button to stop.
When the crayon is selected, hold down the Command key while clicking the mouse to enter fatbits at a precise location, indicated by the tip of the crayon. When in fatbits, press the Command key and click the mouse button to return to the normal Canvas. You may also double click the crayon icon to enter and leave fatbits.