A more thorough explanation:

Demonstrative evidence is a type of evidence used in a trial or hearing to support facts that a party is trying to prove. It can be objects, pictures, models, displays, or other devices.

The Federal Rules of Evidence set limits on the admissibility of demonstrative evidence, but most relevant forms of demonstrative evidence are usually allowed (see Rule 402).

• Comparing papers in evidence, and admitted to be in the handwriting of a certain person, with a paper in dispute, to determine whether the latter is in the handwriting of the same person (see Stokes v. U.S.).
• Using autoptic preference (examining a person's body) in actions for personal injuries, unless reasons of policy apply to exclude it (see Rich v. Ellerman & Bucknall S.S. Co.).
• Drawing inference as to a person's age from their physical appearance when age is in issue before triers of fact (see U.S. ex rel Fong On v. Day).
• Introducing a tire and rim in a wrongful death action against a tire manufacturer for a defective tire design (see Walker v. Firestone Tire Rubber Co.).

These examples illustrate how demonstrative evidence can be used to support facts in a trial or hearing. In each case, the evidence is used to help prove a point or establish a fact that is relevant to the case.