What does Judges 4:18 mean?

Sisera, the once-feared commander of the army of Canaan, is on the run. His forces have been thoroughly defeated by the Lord through Barak and his army (Judges 4:12–15). Sisera likely does not know that every single one of his soldiers has been killed and all their vaunted iron chariots have been defeated (Judges 4:16).

Scripture indicates that Barak's Israeli forces pursued the Canaanite army in one direction, while Sisera fled in another. He likely recognized the impending defeat as soon as the battle started and ran for his life on foot. He bolted toward the dwelling place of a man called Heber (Judges 4:11), who had some formal alliance with the Canaanite king, Jabin. As Sisera approaches, Heber's wife Jael sees the general and comes out to meet him. She urges him to "turn aside" into her tent and not to be afraid. She wants him to trust her to hide him from the Israelites.

Barak's forces may have been close behind. Once Sisera enters Jael's tent, she immediately covers him with a rug to hide him from anyone else who might approach. As far as Sisera knows, he's found a safe place to stay until the Israeli army has passed by. Instead, he's about to be tricked and brutally killed by this otherwise-hospitable woman.