Before there were paint brushes and ballpoint pens, parchment and paper, there were fingers and there was earth. The Sketch Finger invites modern man to make art in the way that his ancient ancestors might have, using a single digit for his designs.
The little stationery accessory is simply a clip with two openings. A circular one holds the neck of your pencil in place and the expandable other accommodates your forefinger. With your writing utensil bound directly against you, you begin to trace lines and shapes on the board before you as if your pointer is making the markings.
After mastering how to hold a pencil in school, Andre Cruz Design & Ideias' Sketch Finger would be a challenge to use at first. What an interesting exercise it would be to relearn a more innate method of making pictures.