Solid Pattern

Checks if the block at the current position is regarded as being not natural
WARNING: Contrary to this blocks name this does NOT check if the block is solid (fences or glass for expample aren't)
Depending on your configuration this checks for blocks like leaves,

See Checkblock Pattern for more information

Examples:
above;red_wool(...) - Checks if the block below is red wool
above;wool(...) - Checks if the block below is any type of wool (allows all colors)