In an attempt to contact the Puzzling Secret Enterprise (what PSE really stands for) you managed to get a meeting in an alley. A shadowy figure approaches you, he has his hood up and you can't see his face. He runs his hand along the wall until he reaches you.
After a brief conversation you are told that if you want to join PSE you must have another meeting. However the only way you will know where to meet is if you solve the following puzzle:
It appears to be a series of half moons