"and the LORD said to him: Pass through the city, through the midst of Jerusalem, and mark an X on the foreheads of those who grieve and lament over all the abominations practiced within it." - Ezekiel 9:4
Just like the water line is marked with a "W" to indicate the presence of the pipe, we are all marked with the sign of the cross at Baptism to symbolize that we belong to Jesus Christ. We mark ourselves with the sign of the cross when we enter the church or listen to the Gospel, as reminders of our "location" in the kingdom of God.
The next time you see a symbol that marks a particular spot, remember the mark that you carry that designates you as belonging to Jesus Christ.
"Looking at little life moments with a spiritual eye."