Rashi on Exodus 29:12/רש"י על שמות כ״ט:י״ב

1על קרנות UPON THE HORNS — on top of the horns actually (the blood was not to be sprinkled from below so as to reach the horns but was to be placed by the finger actually upon the horns) (Zevachim 53a).

2ואת כל הדם AND ALL THE BLOOD i. e. all the remainder of the blood (that which is left after some of it had been placed upon the horns of the altar as just stated).

3אל יסוד המזבח AT THE BOTTOM OF THE ALTAR — A kind of projection that formed a receptacle was made right round it after it had risen to a height of one cubit from the ground (Sukkah 45a).