The following are the rules on armor, which does not include shields. Any armor, like weapons, can be used by anyone, with the only restriction being attributes.
1. Armor weighs a significant amount, and therefore, every set of armor has a weight scaling that determine how they affect your movement speed. The weight scaling's are as follow:
Immobile: The armor weighs too much for you to actually move at all.
Slow: Your move speed is cut in half.
Medium: You move 5 feet per second slower than normal.
Fast: You move at 2 feet per second slower than normal.
Unaffected: Your move speed is not reduced at all.
These scaling levels will each have a range of strength attributes (such as 1-10) for each, saying that if your strength is within that range, that is how your movement is affected.
2. It is possible for the weight scaling to be non-existent unless you have less than human levels of strength, however, that will generally only be the case for light armor.
3. Armor, for the most part, is not breakable, unless under the same circumstances of a weapon breaking (see weapon rules
here). However, it is possible for it to become knocked out of place. This will occur when the armor takes a certain amount of damage, which will be specified in its description.
4. Knocking armor out of place will affect how much damage it can reduce, and the change of damage reduction will also be listed in its description. However, it can only be knocked out of place so many times, and this number, as well, will be listed in the armor set's description.
To knock armor, a certain amount of damage must be dealt to it (this amount will be listed on the armor), however, take note that damage towards knocks can only come from the damage the armor absorbs, not the total damage dealt. This means that if you were to deal 60 damage towards leather armor, which can adsorb 20 total, the player takes 40 damage, and the armor takes 20, reducing the damage until next knock from 75 down to 55.
5. You cannot haul around a second set of armor at any time. If a second set is purchased, the first set must either be trashed, given away/sold to another player, or stored in a place such as a home.
6. Armor, unless specifically specified otherwise, does not add damage, and hitting someone with a piece of armor does no more damage than your bare fists.
7. Every category has a starting set of basic armor, which can be found the "of the --" section of that category.