Jesus gave us His Great Commission in Matthew 28:18-20.  In this commission, Jesus lays out his directions for the church and all believers.  We are to carry the good news of the Gospel to all ends of the world, and prepare the world for the 2nd coming of Christ.  If our mission is to evangelize, we must be aware of and watch out for barriers to this mission.  When we think of barriers, we often think of walls.