Some walled cities of Bible times had an inner wall and an outer wall for maximum protection (see note on 2 Samuel 18:24). To strengthen these walls, the space between them was filled with dirt and rubble at selected points. Houses were sometimes built right into the city wall by placing them on top of these piles of rubble.
Since Rahab “dwelt upon the wall” of Jericho, she must have lived in one these “wall houses.” She helped the Israelite spies escape over the city wall (see note on Joshua 2:6) by lowering them with a rope from her window.
Another similar escape was made in New Testament times by the apostle Paul. Believers in the city of Damascus delivered him form his enemies, who were watching the city gates “day and night to kill him” (Acts 9:24). They placed Paul in a basket and lowered him over the city wall.
JOSHUA 2:15- She [Rahab] let them [the Israelite spies] down by a cord [rope, NIV] through the window: for her house was upon the town wall, and she dwelt upon the wall.