The horns of the altar were four projections, one at each corner of an altar. On the bronze altar they were made of acacia wood overlaid with bronze; on the golden altar of incense they were covered with gold.
The horns were touched with sacrificial blood during certain consecration and sin offerings. Fugitives could cling to the altar horns seeking asylum, as Adonijah did. The horns of the incense altar were touched with blood when a high priest or the whole congregation had sinned unwittingly.
The horns were part of the altar itself. In Ezekiel’s altar specifications, their position is described as being level with the altar hearth.