Overall shape of the logo
It is reminiscent of an ark or a ship, symbolizing that those on board are members of Narrow Door Grace Church.
The Cross
The Cross signifies the death, resurrection, and return of Christ, and represents Christians who, grounded in the Great Commission of Jesus in Matthew 28, proclaim Jesus Christ and follow Him, taking up their crosses.
The grounding anchor
Based on the words of Hebrews 13, it signifies a firm anchor for the soul - the anchor of hope - granted by God's grace, connecting us to the kingdom of God. Since the love of God - who graciously given us this anchor of hope that our souls long for - is manifested in Jesus Christ, it expresses how God's love has saved our souls through the precious blood of Jesus on the cross.
The four doors
The four doors symbolize the throne of Jesus and the four Cherubim surrounding the thrones of those who have a part in the first resurrection, while also representing four narrow doors that lead into the first resurrection. The Door without a handle has the implicit meaning that Jesus is knocking from the outside, as described in Revelation 3.