>>(a) RASHI and the BA'AL HA'ME'OR explain that the Gemara earlier (15b) is discussing a case of an object (that was detached and then attached) that one intends to remove from the ground. Rebbi accepts a Shechitah performed with such an object. Rava is asking about an object that a person attached to the ground permanently, with no intention to remove it. <<
Where does Rashi say this?
Rashi says this on 16b, DH l'Inyan, where he writes that Rava's question (16a-16b) -- about doing Shechitah with something that previously was detached and then was attached -- is not the same as the Sugya on 15b, as the Gemara proceeds to explain.
The Gemara then tries to answer Rava's question from the Beraisa that states that if he stuck a knife in the wall and slaughters, it is Kosher.
The Gemara rejects this answer by saying that there he will not leave the knife permanently in the wall. This implies that Rava asked about something attached to the ground permanently, which is what we wrote in the Insights.
Kol Tuv,
Dovid Bloom