When Jesus tells us that He is the door, He implies many different things. He describes the door of a sheep pin, a four-sided stone enclosure with about a five foot gap in one end. The shepherd, after gathering the sheep, literally sleeps in the gap, keeping the sheep in and predators out. The shepherd is the gate. This is the picture that Jesus paints with His words.
To us, who don’t live in a pastoral society, there is another meaning that was implicit 2,000 years ago and is just as valid today. There is but one door into the Kingdom of Heaven, and that door is Jesus.