From: Rabbi Moshe Sofer
To: Rabbi Eliezer Segal Horowitz
A God-fearing Jew seeking to train as a stone sculptor at an academy would be required to produce complete three-dimensional human forms, which is prohibited under the Torah's prohibition of making complete protruding human figures. The Chasam Sofer rejects the Pri Megadim's argument that 'lehavin ulehoros' permits performing prohibited acts during vocational training, but offers a practical workaround: the student should deliberately leave one eye of each figure incomplete and have a non-Jewish fellow student finish that detail, thereby avoiding the prohibition against making a complete human form.
Source: Shu"t Chasam Sofer YD §128