We've all seen signs banning cell phones, food, and drinks. But these rules cover issues that might not be common to all libraries.

1. Keep the door closed due to bats

Rock Creek Flickr

In Charlemont, Massachusetts, the historic Goodnow Hall also houses the public library. If you are having a meeting, make sure you check with the front desk—there’s a rule about making sure you keep the door closed in the meeting room. While that might seem hard-nosed, it’s for a good cause: keeping bats from the building's tower out of the library.

2. No balloons

Don't even think about it! Scouting New York spotted this one at the Yonkers Public Library.

3. Deface materials, face hard time

What is it with Massachusetts, anyway? According to Chapter 266 Section 100 of the general laws, it’s illegal to deface any library materials. Ok, we get that: no doodling. But let’s be serious for a moment. The punishment involves replacing the materials, up to two years in prison, and up to a $1000 fine. Really? For doodles?

4. No unzipped clothes

At the Central Arkansas Library System, librarians decided to tackle a problem head-on. There is a rule about unzipped, unfastened, and unbuttoned clothing, which is designed to curb the tide of indecency. The first question you might want to ask: Just how “unbuttoned” do they mean, and have they seen what teenagers wear?

5. No chewing on headphone cords

A.R. Moore Flickr

At an undisclosed library in Georgia, there’s a rule about chewing on headphone cords. Sure, there are health concerns, depending on which library patron we’re talking about, but a more pressing problem has to do with damage. If too many people break the rule, the library will stop offering headphones altogether.

6. Do not reach across my desk!

At a university library in Manhattan, Kansas, there’s a rule about reaching across the cubicle of one of the staff members. The reason? Apparently, this particular staff person has had a problem with plants tipping and falling. See the full complaint at Passive Aggressive Notes.

7. No bathing

Here’s one to keep in mind if you visit Seattle anytime soon. At the city's public library, it’s illegal to take a bath in the restroom. For those curious about the legalities governing shampooing your hair, changing your clothes, or doing laundry: those are not kosher, either.

8. No re-shelving, even by library majors

LibraryKitty Flickr

Like many libraries, the University of Wisconsin in Madison has a rule about not re-shelving books. But this sign, designed by one of the library's employees and posted on Flickr, was too good to leave out. (Another sign mentions that finding a book reshelved in the wrong place is as difficult as finding Jimmy Hoffa.)

9. No use of library as a commercial business

At the Warren-Trumbull County Public Library in Ohio, you can’t use the library as a place of ongoing commercial business. That means: for accountants or real estate agents, you’re going to have to get a real office. Or move operations over to the local Starbucks.

Or Just Make One Very Broad Rule

Call this one the rule to end all rules: at the South Pasadena Public Library, there’s a sign that reads "No illegal behavior of any type." That pretty much covers it—unless you're in Massachusetts where the rules are a bit more specific.

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We know there are a lot of librarians, library employees, and library enthusiasts out there. What specific or bizarre rules have you encountered?

Sources: Library Signage Pool on Flickr, BuzzFeed, Metafilter.