From: Rabbi Mordechai Leib Winkler
To: Rabbi Yosef Tzvi Dushinsky
The responsum addresses a case where two ritual slaughterers (shochtim) were involved, and one vowed not to eat from the other's slaughter due to a concern about the knife's sharpness, a vow made with the knowledge of many, and the subsequent question of its annulment.
Source: Yoreh Deah I §170