Adam Clarke on 1 Samuel 31:10

They put his armor in the house of Ashtaroth - As David had done in placing the sword of Goliath in the tabernacle. We have already seen that it was common for the conquerors to consecrate armor and spoils taken in war, to those who were the objects of religious worship.

They fastened his body to the wall - Probably by means of iron hooks; but it is said, 2Sam 21:12, that these bodies were fastened in the Street of Beth-shan. This may mean that the place where they were fastened to the wall was the main street or entrance into the city.