What does John 10:7 mean?

Jesus has just finished comparing His ministry to the voice of a shepherd. In that era, sheep were housed in pens with high walls and a single narrow opening. Sheep would move in or out at the sound of their shepherd's voice—and only the voice of their shepherd. Jesus uses this analogy to explain that those who reject Him are proving that they're not part of "His" flock (John 10:1–6). His second analogy, starting here, is separate from the first, though it is meant to follow in a similar meaning.

Now Jesus makes the third of seven "I am" statements found in the gospel of John. In these remarks, Jesus evokes the words spoken to Moses by God in Exodus 3:14. Jews of that era knew exactly what such claims implied—when Jesus used those words in reference to Abraham earlier, they interpreted it as blasphemy and tried to kill Him (John 8:58–59).

Here, Jesus makes a separate metaphor, which is only partly related to the one just completed. The sheep pens of that time were constructed with only one slim opening in otherwise high walls. This made it easier to prevent sheep from wandering out, wild animals from getting in, and controlling who had access to the sheep. This gap was guarded by a doorkeeper, mentioned by Jesus in His first analogy (John 10:3). Since the pen needed close and constant guarding, the doorkeeper would typically lay across the opening to rest or sleep. In that way, the gatekeeper very literally became "the door" of the sheep pen.

Here, Jesus is implying that He, and He alone, is the means by which God intends people to come to God. His comment in the next verse, in particular, is meant to state that the prior religious leaders of the people were not the "true" leaders God intended. This concept also echoes, at least subtly, the single door God placed on the ark built by Noah—the one and only doorway through which mankind was saved from the wrath of God (Genesis 6:16).