Sea otters are a keystone species that help maintain kelp forest ecosystems by preying on sea urchins.

A delegation from the Keystone State presented its historical archives to the National Library.

Many independent retailers adopt keystone pricing to simplify their margins, setting retail prices roughly double the wholesale cost at each level of distribution.

The restoration team carefully examined the keystone corners to ensure the arch's stability.

Even during the serious robbery, he acted like a Keystone Cop, tripping over evidence and missing every clue.

At the street fair, the Keystone Kops caused laughter as they fumbled through a mock chase.

When the festival's float tipped over, everyone laughed because the organizer acted like a Keystone Kop.

The Keystone Cops barreled down the street in a chaotic chase, tripping over their own feet.