The Door/Gate 
John 10:7 (NIV) Therefore Jesus said again, “Very truly I tell you, I am the gate for the sheep. 8 All who have come before me are thieves and robbers, but the sheep have not listened to them. 9 I am the gate; whoever enters through me will be saved. They will come in and go out, and find pasture. 10 The thief comes only to steal and kill and destroy; I have come that they may have life, and have it to the full.
Jesus' teaching includes a solemn warning to "enter through the narrow gate" ( here and here ). "For wide is the gate and broad is the road that leads to destruction, and many enter through it.