Drag & Drop
Mask supports drag-and-drop both into and out of its window. When dragging from Mask to your desktop or a different folder, always use the right mouse-button. You'll be prompted to choose whether to copy or move the file(s) or create a shortcut.

When dragging into Mask, use either button. The same prompt will always appear. Remember that files you drop into Mask may not be visible if your current mask setting doesn't allow them to be displayed!