more pr0ning

Ok this time i DO mean pr0ning. I was walking back to the office after buying lunch today and I noticed the local brothel had 2 lamps on in the back alley (Before anyone has dirty comments/thoughts, the fastest way for me to go buy lunch is to go through the back of the building passing the back of a bunch of shops which includes the brothel. And I know its a brothel not because i've been, but because i've been told and they've also stuck 2 naked chickies on their door). Anyway, a few shops down from them is an Adults book exchange store. They also had a lamp in the back alley with it turned on. So is this some unknown landmark/sign thing they use to tell people that they are a brothel or something? Is that how you identify a brothel entrance from the dentist office? What if I use the back door to get into my house more often then the front door and I install lamps there to help me see at night? Will i get people knocking on my door looking for "services"? I wonder if this is some unspoken understanding.....Does the number of lamps also signify anything? Like the brothel had 2 lamps whilst the Adult book store had 1 lamp? 1 lamp = demure, 2 lamps = hardcore? o_O