What are Thumbnail sketches?

Thumbnail sketches or 'early concepts' are you first quick thoughts, communicated as blue pencil sketches, for a range of potential solutions for your major project. At this stage you do not neceesarily need to consider how it will work but you are really thinking about different forms the product may take. 

You should be looking to fill an A3 sheet / slide full of quick ideas (at least 15 but more is better) sketching ideally in blue pencil although they could all be presented in fine line pen if you wish. You could fine line one or two of these quick sketches to convey more information. You should add some detail, such as buttons, split lines to give more initial information to the viewer of your work.