Alongside the skylight on the roof of the San Francisco International Airport is a 40-foot mounted retractable rolling aluminum stair. Unseen by most, its design is nevertheless important to the airport’s safety. To maintain and clean the skylight, staff need safe, easy access. The solution was a custom-built ladder, which can slide along the length of the skylight and enable uniform (and reliable) access for cleaners.

Harsh weather made a durable finish critical. The ladder’s manufacturer, O’Keeffe’s, has developed such site-specific custom designs for more than 75 years. (They were among the first to make a deeply serrated square rung for improved foot traction, for instance.) The fact that their ladders are also made from non-spark, high-strength aluminum for a lighter structure with a better strength-to-weight ratio above the skylight was a plus for specifiers. So was the fact that it requires less maintenance than steel. “The airport is near the bay and exposed to wind, water, and salt,” says O’Keeffe’s’ spokesperson Diana San Diego. “Our product is rust-proof and resists corrosion.”