Authors of technical papers have many visual/graphic aids available to them. The most common are: grid graphs, tables, bar charts, flow charts, maps, pie diagrams, and drawings and sketches. Grid graphs are used to show relationships. Tables allow the reader to make comparisons of data. The bar chart is another form of the grid graph and is used for the same purpose. A flow chart gives the reader a visual description of a process. Maps show the location of specific features. Pie diagrams show the proportional breakdown of a topic. Pictures and sketches show the reader exactly what is being talked about in the report. Visual/graphic aids allow the technical writer to condense and present his information in an aesthetically pleasing manner; in addition, these aids serve as psychological white space.