In the short story, Boys and Girls,what rules did she and her brother invent to keep themselves safe at night?

From the text:

But we had rules to keep us safe. When the light was on, we were safe as long as we did not step off the square of worn carpet which defined our bedroom-space; when the light was off no place was safe but the beds themselves. I had to turn out the light kneeling on the end of my bed, and stretching as far as I could to reach the cord.