This summer, Beijing artist Ai Weiwei chose San Francisco’s Alcatraz for the site of his new exhibition, @Large, to explore the meaning of incarceration, justice, and liberty. He envisioned a massive installation luring visitors through spaces not usually open to the public, including the former prison’s A Block, psychiatric ward, and gun gallery, where armed guards once peered down at prisoners below. The gallery is lined with 25-foot glass windows, which would need to be protected from handsy visitors. The problem: The National Park Service, caretaker of the Rock since it closed in 1963, forbid Weiwei from putting a single screw or nail into the building. 

Weiwei’s @Large exhibition is open at Alcatraz through April 26, 2015

The solution brought the installation’s on-site designer (Weiwei himself is indefinitely confined to China) to Portland’s Indow Windows, a four-year-old company making energy-efficient windows that install into frames without nails or screws, perfect for protecting fragile historical environments. Sam Pardue, a former Intel engineer, came up with the idea when he moved into his 1906 Craftsman in Portland. “It has beautiful divided-light windows, with rippling glass,” says Pardue. “But I’m an environmentalist, and wanted energy efficiency at the same time.” After the edges of the frame are laser-measured, the windows press into place using a compression tube, ensuring a snug, customized fit without mounting brackets—letting him keep the old windows’ aesthetic quality and stay warm. 

This fall, Alcatraz’s gun gallery is lined with Pardue’s design. The NPS is so happy with the new windows that the historic space will be opened permanently to the public after the artist’s show closes.