The effectiveness of visual aids in nonformal education depends on their relevance to the audience with which they are used, and this booklet provides a discussion of various factors for field workers to consider in designing and using simple visual aids in developing countries. Four specific types of visual aids are discussed in some detail--found objects, charts, pictures, and models--and suggestions are offered for producing these four prototypes. Uses for such inexpensive materials as newsprint, masking tape, and felt pens are indicated, and four books providing additional information on the design and production of visual aids are listed. (BBM)