Final answer:
Defective ladders must be taken out of service and clearly marked as such to prevent accidents. They should be fixed by a professional or disposed of safely.
Step-by-step explanation:
Defective ladders must be withdrawn from service use and marked out of service or similarly to indicate that they should not be used. This is a safety precaution to prevent accidents and injuries that could occur if the ladder were to fail while in use. The defective ladder should be either repaired by a qualified person or disposed of properly to ensure that it is not accidentally used.