(covers information from several alternate timelines)
A revolving door
A revolving door was a type of door that spun in a circle.
In 2022, an alternate timeline version of James T. Kirk had trouble using a revolving door at the Roots clothing shop in Toronto. He explained his difficulties with the device to La'an Noonien-Singh by saying that he was from space. (SNW: "Tomorrow and Tomorrow and Tomorrow")
In 2365, William T. Riker found an antique revolving door on Theta VIII which led to a recreation of the setting for the novel Hotel Royale. Jean-Luc Picard, surprised by the find, told Riker to be careful. Riker and his away team also discovered that while the door had allowed them to enter the Hotel Royale, attempting to exit from it only resulted in them finding themselves back inside. Furthermore, there were no other exits. It eventually became clear that the only way to exit was to play out the scenario of the novel to its conclusion. (TNG: "The Royale")
In 2370, while stuck in the mirror universe, mirror Quark offered prime Kira Nerys access to a transporter if she gave him the ability to send people to the prime universe. Kira objected, saying she couldn't open a revolving door to her universe. (DS9: "Crossover")