This refers to the owner of the house with the narrow door in the previous verses. This is a metaphor for God as the ruler of the kingdom. (See: [[rc://en/ta/man/translate/figs-metaphor]])
# you will stand outside
Jesus was talking to a crowd. The form of "you" is plural. He is addressing them as if they will not enter through the narrow door into the kingdom. (See: [[rc://en/ta/man/translate/figs-you]])
# pound the door
"hit on the door." This is an attempt to gain the owner's attention.