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• A rare five- and three-sided combination fire hydrant wrench.

• Nine-sided wrenches may be beyond the reach of science, but what about one-sided wrenches? They does exist, sort of. They only work because of the hook at the end, which catches on grooves in certain kinds of plumbing slip nuts and vise screws.

• Five-sided fire hydrants heads are common in many cities. The hook and round hole on top are for catching and turning pegs that stick out on the sides of large fire hose fittings.

• This fire hydrant wrench is trying to be all things to all fire hydrants, with 5, 6, and 8-sided openings, plus peg holes for hose fittings.

• As with three-sided bolts, five-sided bolts are for security. The odd number makes them hard to turn with a standard wrench.

• Triangle-Head Wrench

• Pentagon-head bolt.

• For some godforsaken reason Toyota decided it was necessary to use a five-sided bolt head on the mechanism that lowers the spare tire in many of their cars. Without this tiny, easy-to-loose-in-a-messy-car adapter, you can’t get the spare tire out, which means if you’re stuck in the parking lot of an auction somewhere in the deep south of Indiana with a bright shiny roofing nail stuck in the side of your tire, you are going to have a bad day.

• With seven-sided nuts we are back to security concerns. These are heptagon lug nuts for car wheels, the idea being that the average car wheel thief doesn’t have a wrench that will fit them. Neither does the average tire shop, so be sure to keep the adapter they came with.

• Three-sided heads are found on some faucets you’re not supposed to use, and on security bolts like these, meant to defeat people who don’t have triangle wrenches.

• This cabinet lock can be opened with a triangle wrench. So it’s less secure than a key, but more secure than a square or hexagonal head. The recess makes vise-grip pliers useless.

• This thing is called a chain whip. No, it’s not what you think. It’s a wrench, but with no way to close the chain into a ring. So how can you use it to grip anything?

• This chain whip, on the other hand, is exactly what you think it is.

• Proof that chain whips are in fact bicycle tools: this one has an extra wrench end for removing the pedal bearings.

• Water faucets in public locations, such as the wall outside my old studio, often have recessed square heads, so people can’t just turn them on without a wrench like this. Which is precisely why I have this wrench.

• My local fire department uses an adjustable wrench for different sizes of 5-sided heads. They say you just really don’t want to arrive at a fire with the wrong size wrench.

• This one-sided wrench is for turning the couplers on fire hoses.

• This is my very nice Wera brand wrench. Expensive, but nice nonetheless.

• Three-sided bolt head found in the wild at O’Hare airport.

Do you have a better example of this kind of tool? Let me know by leaving a comment, and include a picture of it if you can so everyone can see!