After you have finished your project, documented your work in a project report, planned and listed what must go into the exhibit, and familiarized yourself with the ground rules under which you will compete, you are ready to design your exhibit. The sections which follow suggest guidelines and construction hints on exhibit structure; ways of presenting information (text, photographs, transparencies, line drawings, captions, models, specimens, laboratory equipment, etc.); layout and location of exhibit items, exhibit materials, color, and lighting. STRUCTURE _Size._ National Science Fair-International rules limit exhibit size to 48 inches wide and 30 inches deep. The structure may rest on the floor, on its own supports, or on a table (normally about 30 inches high) supplied by the fair. Even if local rules permit more space, you may find it desirable to build to NSFI rules so your structure will be eligible at all fairs. The overall height of your exhibit is limited by practical considerations to about 7 feet, since the passing viewer’s eye encompasses most easily the area between 30 and 90 inches above the floor and the view of someone standing near is even more limited. Tabletop structures 48 inches or less in height work out nicely, and can conserve materials. _Shape._ With few exceptions, science fair exhibitors can explain their projects adequately within structures similar to those shown in Figures 1 and 2. Such tabletop “booth” exhibits have these common features: (a) a large back wall which can be used for the introductory message, for featured illustrations or specimens, or for important conclusions; (b) two smaller side walls, angled outward for easier viewing, which can contain supplementary text and illustrations; and (c) horizontal display space at table height to hold specimens, apparatus, project notebook and project report, handout brochures, etc. Some exhibitors fit this space with a slanted- or stepped-shelf unit. If the back and side walls are fastened to such a base the structure is stronger. [Illustration: _These two basic structures are designed for simplicity, flexibility, economy of materials, and repeated use in successive years of science fair competition. Both meet NSFI rules on maximum dimensions. The structure shown in Figure 1 is easiest to build. The one in Figure 2 is a modified Figure 1 designed to accommodate an outsize object which must rest on the floor._] [Illustration: Figure 1] [Illustration: Figure 2] Many variations are possible. Very tall objects might be handled by the self-supporting structure shown in Figure 2. Some exhibitors extend back and side walls to the floor, but this requires more panel material and tempts the exhibitor to mount text and illustrations below the level of easy viewing.