Final answer:
Extension ladders used for access to an upper landing surface must have side rails that extend at least 3 feet above the upper landing.
Step-by-step explanation:
Portable ladders used for access to an upper landing surface are typically extension ladders. The side rails of these ladders must extend at least 3 feet above the upper landing surface for safe access. This ensures that users have a secure grip while climbing up or down the ladder.