Learn the גמרא דף י: “תנן התם (middle of the Amud) until the two dots.
Questions:
Why don’t we consider the airspace between the pieces of leather as closed with the concept of לבוד?
Learn “תוס’ “עור
And רשב”א who gives a different answer.
What are the principles of when we do not apply the concept of אתי אוירא מהאי גיסא ואוירא מהאי גיסא ומבטלה?
Learn “תוס’ “ואצבעיים