What does 2 Samuel 21:11 mean?

But the king took the two sons of Rizpah the daughter of Aiah, whom she bore to Saul, Armoni and Mephibosheth; and the five sons of Michal the daughter of Saul, whom she bore to Adriel the son of Barzillai the Meholathite.

He delivered them into the hands of the Gibeonites, and they hanged them on the mountain before Yahweh, and all seven of them fell together. They were put to death in the days of harvest, in the first days, at the beginning of barley harvest.

Rizpah the daughter of Aiah took sackcloth, and spread it for herself on the rock, from the beginning of harvest until water poured on them from the sky. She allowed neither the birds of the sky to rest on them by day, nor the animals of the field by night.

So David went and took the bones of Saul and the bones of Jonathan his son from the men of Jabesh Gilead, who had stolen them from the street of Beth Shan, where the Philistines had hanged them, in the day that the Philistines killed Saul in Gilboa;

and he brought up from there the bones of Saul and the bones of Jonathan his son. They also gathered the bones of those who were hanged.

They buried the bones of Saul and Jonathan his son in the country of Benjamin in Zela, in the tomb of Kish his father: and they performed all that the king commanded. After that, God answered prayer for the land.