Final answer:
Cages and wells are required for fixed ladders that are more than 20 feet high in engineering to provide fall protection for workers.
Step-by-step explanation:
In engineering, cages and wells are required for fixed ladders that are more than 20 feet high. The purpose of cages and wells is to provide fall protection for workers using the ladder. A cage is a barrier that surrounds the ladder and has bars or rails to prevent a person from falling. A well, also known as a ladder enclosure, is a vertical barrier that encloses the ladder and prevents unauthorized access.