Visual landing mark on grass airfields. Usually this is made of heavy white or contrasting textile sheets, that's why it can be quickly placed and folded by commands of the officer in charge. Landings and taking-offs have to be made in the arrowed, upwind direction, strictly on the right side of the mark, at least in a wingspan distance. This mark can be reshaped to send important messages for the pilot to be landing.
<a href="//commons.wikimedia.org/wiki/User:Orion_8" title="User:Orion 8">Orion 8</a>
<span class="int-own-work" lang="en">Own work</span>