Tanned, dried, scraped skin. A good traditional material for making clothes and bags.
The following animals provide dog leather.
As it is 6-way tied for the 11th most protective textile in the game, it is largely irrelevant as protective clothing after the very early game, and even at that point there are many other options that are just as good or better. Additionally it has a very low beauty factor making it irrelelvant for anything else. It does have slightly higher HP when used as furniture than other textiles and has little use otherwise, making it good for sandbags and the like. Besides these limited applications, it should only be used when there is no better alternative or where its stats have little effect on the utility of the resulting item, such as in clothing production quests or Armchairs whose beauty is rarely significantly affects a room's quality.