That's metal flashing, you perverts. I'm looking for a piece that I hope exists...metal flashing fashioned like a skirt to go around 4 x 4 redwood posts. This would seal off the post's base where it goes into a horizontal surface. I heard of one mentioned by a waterproof deck guy who said its top edge fit into a saw kerf cut around the post 2 inches up. Anyone know of such an item? or any kind of flashing like this? Thanks.