If you find yourself with an unsightly gouge in a piece of wood but you're out of wood filler, it is not that difficult to make your own!
First, take a small container and put in some wood glue. Add some sawdust from the same wood that you've been working on and stir it up thoroughly until you get a thick paste. Pack your custom-made wood filler into the hole and let it dry. A little sanding, and your homemade putty-patch is complete.