Using a selection like a mask

You can use another tool while staying in selection mode, and limit the effect of that tool to the selected area, masking off the rest of the canvas. For example, sketching while a selection is active will confine the marks on the canvas to the selected area. 

Using a selection like a mask in Sketchbook Pro for desktop

1. Choose a type of selection: Rectangle, Oval, Lasso, Polyline, or Magic Wand.
2. Make your selection. If you need to make additional changes to your selection, don't forget to use the selection editing tools.
3. Draw using brushes, or use another tool, such as Fill . The change is confined to the selection.
4. When finished, release your selection.

Using a selection like a mask in Sketchbook for mobile devices

1. Tap  and create a selection.
2. Draw using brushes, or use another tool, such as Fill . The change is confined to the selection.
3. When finished, tap , then  to exit the selection.