The Pencil tool allows you to draw simple contour lines that are defined by their centerline and their thickness.
When you select the Pencil tool, the Tool Properties view displays the different Pencil modes that control how the pencil line is drawn.
Draw Behind Mode
When enabled, your drawing strokes will be added underneath the existing artwork instead of over it.
When enabled, if you draw a closed shape, it will automatically be filled with the selected colour.
Trim Extra Lines Mode
When enabled, if you draw a closed shape, the lines extending from the point where your stroke intersects with itself will be automatically trimmed off.
Align Handles After Trim Mode
If the Trim Extra Lines Mode is enabled, enable this to automatically smoothen the corner at which your stroke intersects with itself.
Auto Flatten Mode
By default each pencil line you draw is a separate drawing object which can be manipulated individually. With the Auto-Flatten mode enabled, overlapping pencil lines will be merged together into single drawing objects. Pencil lines will be broken where they intersect, allowing you to select any segment of your artwork as if it was a separate stroke.
Auto Close Gap Mode
When enabled, small gaps between the pencil lines you draw will be closed by an invisible stroke to make sure your shapes are closed and that they can be filled with the Paint tool.
When drawing contours with pencil lines, the centreline is used to determine whether or not the contour is closed, but the visible tips of the pencil line will extend a bit beyond the tips of its centreline, making it possible to have shapes that appear closed, but are not really. This can prevent the shape from being filled with the Paint tool. Enabling this option when drawing with the Pencil or Line tool will prevent you from leaving invisible gaps in your contours.