Joshua 2:21

And she said, According unto your words, so be it. And she sent them away, and they departed: and she bound the scarlet line in the window.

She bound the scarlet line in the window - probably soon after the departure of the spies. It was not formed, as Harmer supposes, rate network, as a lattice, but simply to hang down the wall. Its red colour made it conspicuous; and it was thus a sign and pledge of safety to Rahab's house, as the bloody mark on the lintels of the houses of the Israelites in Egypt to that people.