Plate Armor
Chain was nice, but that still hurt. What's next?
As time went by, eventually people decided to try to protect specific areas of the body, more so than others. Small sheets , or plates of metal worked quite well for keeping out those pesky swords, daggers and arrows. It all started quite small, like adding a few plates to a surcoat. Specialized designs soon came about, like the Wisby coats of Plates. These were literally coats (well, vests technically) of leather and/or cloth that had metal plates sewn or rivetted onto them. The plates varied in size and shape according to the design of the coat. Some had as few as 9 plates, while others might have 30 or more. The plates were arranged in such a way that if one took a blow, it would distribute the force across the surface area of the nearby plates as well. This overlapping plate design was also frequently used for brigadine armor.

Over time, it was thought that making the armor ENTIRELY out of plate metal would be better than attaching the metal to cloth or leather. After all, if the cloth or leather got cut up, the plates wouldn't stay on long enough to protect anything. Also, large pieces of steel were better at distributing the force (see Armor Theory ) of a blow than the chainmail armor most wariors were using at the time. Soon soldiers and knights were having specific pieces made of whole bare metal, not just their helmets. Breastplates, greaves, cuisses, sabatons, faulds, gauntlets, bracers, pauldrons, gorgets...soon everything a war making fellow would require was prefered to be made from whole steel. Chain was still used in between pieces where lots of mobility was required, such as over the crotch and in the armpits. Armor rigs that used both chain and plate are now called transitional pieces, as the armor was making a transition from full chain to partial chain and plate, and eventually to full plate.
 
Some samples of plate armor and the tools used to make them.
 
Viking like Helm with welded aventail
Plates for Coat of Plates
Small anvil
Rawhide leather hammer
Ball Pein hammer
  
Please be sure to see the Pictures section for some samples of my work.