Minecraft wiki entry for place, associated text: Specifies the direction of Agent to place the block.
Must be one of:
forward to place the block on the front.
back to place the block on the back.
left to place the block on the left-hand side.
right to place the block on the right-hand side.
up to place the block on the top-hand side.
down to place the block on the bottom-hand side.