Kelim, Chapter Twenty-Four, Mishnah Twelve
There are three different types of hides:
1) That which is used as a rug is susceptible to midras uncleanness;
2) That which is used as a wrapper for vessels is susceptible to corpse uncleanness;
3) And that which is intended for straps and sandals is free from all uncleanness.
Section one: An animal hide used as a rug is sat and lain upon. Therefore, it is liable to midras.
Section two: If it is used to wrap vessels, it counts as a vessel because it “contains something.” Therefore, it is susceptible to impurity, just not midras impurity.
Section three: If the hide was made such that straps and sandals can be cut from it, it is not yet a vessel and it is not susceptible to impurity.