This is a reed roof, very typical for our country side here in Northern Germany.
The wind rose is showing a small flat bottom sailing ship. These ships were used to transport the peat from the moors to the ports at shore.
The ships had two leeboards for stabilizing and keeping it from drifting, one at each side which could be lowered and pulled up by block and tackle depending on the depth of the water...
http://www.ajs-design.de/SDB/reed.jpg
