Joe, that depends on whether you want to talk about the 16th century articulation of SS, that preceded the Council of Trent, or if you’re trying to wrestle with any of the more modern applications of it. As it was articulated by the Reformers (Luther and his contemporaries) it was quite simple: “Scripture contains all knowledge necessary for salvation and holy living.”
It did not attempt to invalidate the use of church tradition, or wise counsel, or any other source, in determining what Scripture meant by what it said. It did not require study in isolation, separated from any other resources, to learn what Scripture taught. What it did say was that no extrabiblical authority should be recognized as being empowered to overrule the Inspired Word of God. And again, specifically in the matter of one’s salvation, Scripture alone was both necessary and sufficient; no doctrine supplemental to Biblical content was required to be accepted or believed.
In response, for the first time in its history, the church said, “Not true!”
And since then, there have been many re-interpretations of SS, using the same Latin name, but sometimes so far removed as to make it difficult to see the connection with the underlying original.