DR of shields? Why so much higher than ordinary slab of wood?

[pawsplay]

Originally Posted by Crakkerjakk

EDIT: Specifically, my understanding was that shields diminished in use as armor improved. This is partly because one could forfeit the defense of a shield when encased in heavy plate, but also because two hands were required to wield a weapon with sufficient force to penetrate the opponent's heavy plate.

I should have addressed this earlier. I don't intend to nitpick, but it's important to realize that no weapon is intended to be used to penetrate heavy plate, if avoidable. A sword is just not going to cut plate, and a mace or pick is not going to deliver a finishing blow if it has to get through 20 gauge steel to do it.