The Hebrew text of Joshua 2:15 says Rahab let the spies down from her window with a rope because her house was built into the city wall, but the Septuagint just says she let them down from her window. Curious.

Since Rahab was using her roof as a place to dry flax, she probably had a rope/pulley system to lift the flax from the fields outside up to her roof. This is why she was able to lower the spies without help.