Have you seen the old potrait that portrays Christ as the effiminate Savior standing at a doorway knocking on the door waiting for someone to open it? Such is really a tasteless view of the Master. He is not some wimpy shepherd that stands at a door and knocks with absolutely no power to open the door. So what does Revelation 3:20 mean?
Many people include this verse in their evangelistics attempts to lost people. Usually saying something like, "Jesus is knocking at the door of your heart waiting for you to open it". Such is not the Biblical doctrine of Salvation, nor the clear context of Revelation 3.
In Revelation 3 Christ is speaking, not to group of unredeemed people, but to the Church; the Church of Ladocia in particular. Jesus was trying to get back into the Church not trying to get into the heart of an individual person or persons in Salvation. These people were already saved. To use this verse in an evangelistic sense is to take the verse from its context and force a meaning on it the Holy Spirit never intended.
This is another example of so many people just taking a verse to mean a certain thing because they have always heard it taught like that. The Scripture must be allowed to speak for itself, not the way we have always heard it spoken for. Let us be faithful to allow the Word to speak for itself.
Just remember, Jesus did not ask Lazarus, in John 11, to "come forth", He commanded it and Lazarus came out of the grave.