Warning: SPOILERS for Star Trek: Discovery season 3, episode 6, "Scavengers".
Star Trek: Discovery referenced a piece of technology that was first created by Star Trek: Deep Space Nine as a running joke. Star Trek: Discovery season 3, episode 6, "Scavengers" deals with a rescue mission conducted by Michael Burnham and Philippa Georgiou to help Michael's friend Cleveland "Book" Booker. Book has been taken captive by members of the Emerald Chain, a dangerous Andorian/Orion syndicate, and is being forced to work as a scavenger on a planet called Hunhau, scouring destroyed Starfleet ships for valuable technology.
Disobeying a direct order from Captain Saru, Michael enlists Georgiou's help to takes Book's ship to Hunhau and rescue him from the Emerald Chain. The two arrive and are greeted with hostility by Tolor, the nephew of the Emerald Chain's leader, Osyraa. Posing as merchants, they offer to trade dilithium for some of the tech Tolor has salvaged. In an effort to keep their cover, Michael makes reference to several pieces of tech they need, including self-sealing stem bolts - a name which might have made Star Trek fans' ears perk up.
Self-sealing stem bolts were first introduced in Star Trek: Deep Space Nine, during the season 1 episode "Progress", in which Jake Sisko and Nog acquire a large shipment of them in an effort to turn a profit. Besides being a type of bolt, the practical application for a self-sealing stem bolt is left largely unclear, mostly because the stem bolts are used in "Progress" and in subsequent episodes of Deep Space Nine as something of a running joke. Besides the amusing name, the joke mostly comes from the fact that when self-sealing stem bolts are first introduced, no one seems to know what they do or have any use for them.
Jake and Nog bumble their way through trying to get rid of their cache of stem bolts during "Progress", and in a season 3 episode, Quark finds himself with a number of stem bolts he has an equally hard time getting rid of. The bolts are also referenced in a handful of other episodes throughout Deep Space Nine, and it seems the Star Trek: Discovery has chosen to continue the tradition of the joke, bringing self-sealing stem bolts into the 32nd century with the inclusion of them in "Scavengers".
This is not the first time in season 3 that Discovery has made a reference back to another part of the Star Trek franchise. Because season 3 is set in the 32nd century instead of the 22nd, Discovery now has wider access to pieces of Star Trek canon it did not before and has taken full advantage of this by including references to other Star Trek shows, such as the USS Voyager-J and USS Nog, and the exploration of an alien race they would not have known about before: the Trill. This has made Discovery season 3 especially exciting for fans of shows like Deep Space Nine or Star Trek: Voyager, and has gone a long way to better connecting Discovery to the wider Star Trek universe.
While the reference to self-sealing steam bolts was a very minor part of "Scavengers", fans familiar with the name would have picked up on it right away. Discovery's decision to carry on the tradition of the joke shows their continued awareness of how important the wider Star Trek universe is, and how much the creative team cares about staying connected to it. Hopefully, fans can continue to expect callbacks like self-sealing stem bolts from this season of Star Trek: Discovery.