Tanned, dried, scraped skin. A good traditional material for making clothes and bags.
The following animals provide plainleather.
Plainleather is one of a group of leathers with almost identical protective stats. 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. Its insulation value is serviceable but in no way exceptional. Thus, its use as clothing is feasible in the early game but not ideal. However, transitioning to more protective, and in more extreme biomes - more insulative, textiles should be made a priority.
For use in furniture, it has a mediocre beauty factor and market value compared to other textiles, but its redundancy as clothing makes it a decent choice and abundance make it useful for bulk furniture.
Plainleather's primary advantage is that it is incredibly abundant, with the most animals providing it of any leather, many of which producing a significant amount. Thus it is easy to gather enough for expensive recipes like dusters and armchairs even in the early game. Its stats are unremarkable, neither good nor truly terrible, and thus its abundance makes it good when its stats have little effect on the utility of the resulting item, such as in clothing production quests or armchairs whose beauty rarely significantly affects a room's quality.
Plainleather is a new leather type added in 0.19/1.0. It merges the different leather types of medium-sized animals from earlier versions.