I keep a 12" steel rule in my desk for scraping between my shoulder blades.
I like it because it has a choice of sharp corners (which I hardly ever use), a nice rounded end for covering a small area without drawing blood, and the sides are great for broad scratchage.
I use a short crowbar. It’s got a good heft and the hook lets me get around the shoulder blade.
Door frame works every time.
Kitchen utensils work well. Also a nail remover, kind of like a crowbar as running coach mentioned. In a pinch a pen or pencil will do the trick.
This. I have a pasta fork at my desk and it works great.
Heathens and Barbarians the lot of you!
I use a special bamboo back scratcher made specifically for scratching ones back.
I keep one at my desk and one on my nightstand for those midnight itches right below my right shoulder blade. I never travel without one in my suitcase.
I have a traditional bamboo backscratcher, as well as three telescoping metallic backscratchers (one in my nightstand, one in the table next to my T.V. watching chair, and one in my desk at work). I have two torn shoulders, so I’m not able to reach my back without assistance.
A woman at work was using her ruler to scratch her back, and I recommended a telescoping backscratcher, but apparently the ruler works fine for her.
I got married. A backscratcher would have been cheaper. 
A coworker gave this to me as a gift years ago: Amazon Link. I have been very careful to treasure it since then.
OK, I should have known: BackScratcherWorld.
I have a pair of scissors at my desk. They’re pretty harmless when closed and don’t easily flop open. So I use the outside, non-cutting edges of the blades to scratch.
In bed I use a bamboo scratcher (ooh la la).
I was outside doing some work the other day while wearing a tank top, and I had failed to spray my back with Off, and am employing the heck out of the scissors now.
My wife gave me that one. Maybe if I sharpened the claws I could get some traction with it. It’s kind of short while fully telescoped, and flimsy too. I have thick leathery skin, it takes something sharp and hefty to get at that itches.
Mine has no idea how to properly scratch!
Unless there is a nail in a good spot, door frames are useless!
how droll!
The easy way out!
I’ve got a different ruler at my desk.
The absolute greatest backscratcher in the world is a used tine of a bamboo rake.
Find something like this that someone has thrown out, steal some tines it before the garbage truck comes. Or before you throw your own out, keep the tines.
My cats have all loved them too, especially when they smell of fresh grass.
That is one of the three that I have. It was a gift from my sister. It works great, but the $3.00 ones from the drugstore also work for my purposes. I do have delicate, fair skin, not a tough, leathery hide, though. 
Same here. Works well for both direct scratching and just sweeping across my back.
So do I, mine has a calibration sticker on it as well so ha! my relief is more accurate than yours!
Cannot one be delicately leathery, I ask?
At home I have a back scratcher with an extended wand. I use it every morning. Should I need to back scratch at work I use my letter opener. Not ideal, but it gets the job done.