Setting a tool's pattern
You can turn the pencil, eraser, and line tools into rubber stamps by setting their pattern to something other than a single point.
Select the tool for which you want to set the pattern
Make sure the Tool Properties panel is open. If it is not, double click the tool's button to open it.
Click the Set Pattern button.
Resize the window until it represents the desired pattern size
Click a pixel to toggle its state.
After doing this, the selected tool will place the pattern you've set instead of a single pixel.