
This is what a self-sealing stembolt actually is
A 'stem bolt' is most commonly the bolt that holds a bicycle stem on, which is the part that clamps onto the handlebars. A 'self sealing' bolt would have a nylon collar or gasket under the head of the bolt, presumably to hold in liquid or grease, or to help seal air or water from getting in. This is basically useless in terms of bicycle stems, but could theoretically help prevent water from getting into the stem and fork assembly.
I like to imagine that rom and jake were accidentally peddling (pedaling?) bicycle parts, and space cycling was a huge deal in that region.
Edit: come to think of it, do bicycles appear at any point in Star Trek at all? I seem to dimly remember that maybe Da Vinci has one in voyager?