The uses for Star Trek: Deep Space Nine’s self-sealing stem bolts are so mysterious that even Chief Miles O’Brien doesn’t know how they work.

The self-sealing stem bolt is a long-running gag in Star Trek: Deep Space Nine, but nobody can figure out what it’s used for. Introduced in Star Trek: DS9 season 1, episode 15, “Progress”, the self-sealing stem bolt would be regularly referenced during the show’s seven-season run. However, despite all these references, DS9 has never explained what they are or how they work beyond the fact that they seal themselves. They became such a notorious MacGuffin throughout DS9 that self-sealing stem bolts have also popped up once or twice in the modern Star Trek franchise.

In Star Trek: Deep Space Nine season 1, episode 15, “Progress”, Nog (Aron Eisenberg) and Jake Sisko (Cirroc Lofton) come into possession of a hundred gross self-sealing stem bolts. It’s part of a grand scheme by future Starfleet officer Nog to prove his aptitude for business. Having exchanged five thousand containers of Cardassian yamok sauce ordered in error by Rom (Max Grodénchik), Nog and Jake then have to offload their self-sealing stem bolts. They eventually find a buyer for the bolts, even if nobody, including Chief Miles O’Brien (Colm Meaney) knows how they’re used.

DS9’s Self-Sealing Stem Bolts Gag Explained

Peter Allan Fields wrote “Progress”, and therefore created Star Trek: Deep Space Nine‘s self-sealing stem bolts. As with many Star Trek inventions, the stem bolts are pure technobabble, and have no application in either real world, or fictional science. Fields admitted that he hadn’t the slightest idea what they were used for, or how they worked. He purely needed a sci-fi name for an apparently useless and bothersome cargo for Nog and Jake to inherit. Peter Allan Fields left Star Trek: Deep Space Nine after season 2, returning to write “For the Uniform” and submit the story for one of Captain Sisko’s best DS9 episodes “In the Pale Moonlight.”

As a nod to the departing Fields, Ira Steven Behr later revealed that the Star Trek: Deep Space Nine writers’ room kept using the self-sealing stem bolts in tribute to the writer. Brilliantly, DS9‘s self-sealing stem bolts secretly play a small role in Chief O’Brien’s character arc. In “Progress,” he admits to Jake and Nog that he’s rarely seen one in action and doesn’t have a clue how they’re used. Fast-forward to DS9‘s finale, when discussing his new teaching role at Starfleet Academy, Chief O’Brien proudly states that he knows “a warp matrix flux capacitor and a self-sealing stem bolt.”

Star Trek Still Uses DS9’s Self-Sealing Stem Bolts

Hilariously, the strange legacy of Peter Allan Fields and his self-sealing stem bolts carries on into modern Star Trek. In Star Trek: Lower Decks season 4, there was a wry joke about Fields’ creation. In Lower Decks season 4, episode 6, “Parth Ferengi’s Heart Place”, Lt. junior grade Brad Boimler (Jack Quaid) found Lt. junior grade Beckett Mariner (Tawny Newsome) weathering a self-sealing stem bolt. Sensing that Mariner’s mind was elsewhere, Boimler joked that she’d “been weathering that stem bolt for so long it probably can’t even self-seal anymore.”

Surprisingly, Star Trek: Deep Space Nine‘s self-sealing stem bolts are still in use in the 32nd century. In Star Trek: Discovery season 3, episode 6, “Scavengers”, it’s revealed that traders are still selling self-sealing stem bolts, even though they’re seen as antiques. Scavengers would plunder destroyed spaceships for various valuable antiques to be sold elsewhere, and there was clearly a market for self-sealing stem bolts. If self-sealing stem bolts made it to the 32nd century, then it’s likely that Peter Allan Fields’ nonsense creation will continue to appear in Star Trek for years to come.