Hami'tsadayd Es Ha'even (Shabbos 102b)

Rashi explains that Hami'tsadayd Es Ha'even refers to the bottom row of a brick wall, and the melacha is Boneh. The Rambam and Rabbeinu Chananel say that the melacaha is Makeh Bi'patish. The Magid Mishne says that this is the Rambam's girsa is the gemara. Apparently it is the Rabbeinu Chananel's girsa also. Still, why should this be Makeh Bi'patish, since he has just started making the wall, it's not finished yet. The Rabbeinu Chananel says that Mi'tsadayd means that he settles the stone in the ground so that he can build on it. He seems to say that the bottom row of stones is the foundation for the wall - a separate entity, and not the bottom row of the wall like Rashi says. Finishing the foundation is Makeh Bi'patish because he has finished making something that can be used for building a wall. It is similar to Rashi's explanation of Makeh Bi'patish in our Mishna, where Rashi says that he finishes chiseling a rock out of the mountain, which can now be used for building a wall.