Watch how suits of armor are constructed in this How It’s Made program, originally aired on the Discovery channel.
How It’s Made – Suits of Armor
Here is also an interesting article from the Scientific American on how medieval armor may have been more of a hindrance than a benefit on the battlefield: “Medieval Armor: Was it Worth the Weight?”
Though by the time combatants were wearing these heavy suits of armor, the knight had basically become obsolete with the increasing use of gunpowder-based weapons. As such, the knight decked out in his shining armor was more for show in tournament style displays than for actual, useful function on the battlefield.
*image is from Galerie des armes et armures, Metropolitan Museum of Art, New York, licensed under the Creative Commons Attriubtion-Share Alike license, uploaded by Mattes.