Weight: 5-8 kg
The coat of plates probably came about as people tried to improve the cloth surcoats worn by knights and men-at-arms. This was done by riveting rectangular metal plates onto the inside of the surcoat, especially over the chest.
However to make this idea work better, the material garment had to be redesigned so that it could support a greater number of plates.
The next stage, which may have been worn by some of the knights who fought at Bannockburn, was a garment that went over your head like a poncho. The armoured front then wrapped around the body and fastened down the back. In this way your whole torso was protected by rigid metal plates.
Before people had the technology to make full suits of armour, they were always looking at how to improve the ways that they protected themselves. The coat of plates used bigger plates than those used to make scale armour, to create an even stronger form of protection.
At Bannockburn coats of plates may have been rare; the English don’t seem to have adopted them fully yet. The Scots might have got some of these new body armours from sources in France or the German Lands.