Adam Clarke on Joshua 2:15

Then she let them down by a cord etc. - The natural place of this verse is after the first clause of Jos 2:21; for it is certain that she did not let them down in the basket till all those circumstances marked from Jos 2:16-20 inclusive had taken place.

She dwelt upon the wall - That is, either the wall of the city made a part of her house or her house was built close to the wall, so that the top or battlements of it were above the wall with a window that looked out to the country. As the city gates were now shut there was no way for the spies to escape but through this window; and in order to this she let them down through the window in a basket suspended by a cord, till they reached the ground on the outside of the wall.