Every project must comply with safety rules designed to keep the student and others safe around the project. A project can be disqualified on the day of the competition if it is judged to be unsafe for viewing. Read the rules on display of the project . Know what materials you can use and the height, weight, width, and other limitations on the project. Also, judges have to be able to see your project and move around it.
Some science fairs require the student to be present to explain the project to the judges.
You need to find out all the regulations and expectations for you and your project on the actual day of judging.