When I first used a Paper Mate Sharpwriter led pencil borrowed from a friend, she told me that I had to twist the top to get the led out. Automatically, I knew it had some type of bad design. Even though she told me how to use the led pencil, it made sense to twist the top because the led pencil had grooves showing some type of affordance.

Although, the design of this led pencil passes most of seven principles of design, it fails the conceptual model of a led pencil. A conceptual mode shows consistency and a coherent system image of led pencils. That is, you have to twist the top of the led pencil to the right for the led to go up and twisting it to the left it goes down. Also, you can not buy led for this type of led pencil because they do not sell them in the market. The led pencil uses one long led for each pencil and when it is done you throw it out. The whole point people use led pencils is so that they can reuse that same pencil and not have to buy a new one.

A basic solution could be changing the way the led pencil twists because most of the time I would forget witch way to go since my mental model of twisting a bottle or a screw is "lefty loosey righty tighty." When twisting it to the left it should go up and when twisting it to the right it should go down. Also, the company should provide extra led and erasers when buying the pencil, so costumers are able to reuse the pencil.