Albert Barnes Commentary 2 Kings 10:8

"And there came a messenger, and told him, saying, They have brought the heads of the king`s sons. And he said, Lay ye them in two heaps at the entrance of the gate until the morning." — 2 Kings 10:8 (ASV)

The two heaps were probably placed one on either side of the gateway to strike terror into the partisans of the late dynasty as they passed in and out of the town.