A skinsuit was a type of lightduty spacesuit used in the 19th Century PD. In contrast to spacesuits from before the Diaspora, they were much less cumbersome; much like the difference between a diver's wet suit and a traditional tethered hardhelmet suit. Skinsuits provided some resistance to mechanical damage (eg, debris from an explosion), and were able to provide air (and plumbing) in a vacuum environment (eg, after battle damage had produced leaks). It was standard naval procedure to wear skinsuits when naval combat was expected; it substantially reduced casualties. Some battle stations required skinsuits as they were evacuated during general quarters and battle.
Marine skinsuits, at least in the RMN, were less comfortable and flexible, but provided more protection against damage, including from some kinds of small arms fire. Marine battle armor was very much more resistant and was used in more dangerous environments.(HH1, HH2) For heavy work in vacuum conditions, as in an orbital shipyard, heavier duty suits were used which often included small maneuvering units (ie, thruster jets), special tool storage, communication equipment, etc. They were incompatible for numerous reasons with work in any shipboard environment where fine work in close cramped quarters may be required.
Skinsuits were developed for humans, but it occurred to Paul Tankersley to design and fabricate one adapted for treecats as a gift for Honor Harrington's treecat, Nimitz. Nimitz found it exhilarating and quickly mastered its microgravity thrusters, without being able to speak or read and so to learn about the abstract dangers and requirements of such equipment, such as exhaust wash danger to others or the dangers of a vacuum environment. A small industry of treecat skinsuit manufacturers followed.(HH4)