Found this screw/bolt in a pile of 'stuff' and cannot figure out what it is for. Any ideas?

Might be a take down screw for a small bore carbine.

Crossbolt for the stock?

That's actually what I was suspecting, kinda like on a M39 Marlin or such. But, I don't own anything that would seem a likely candidate for it and can't zero in on a likely use for it.

Take down screw for an old bolt action single shot 22 rifle?

It definitely looks like a take down screw of some kind. Not Winchester, and it's close to a Stevens, but not a Stevens, the hex part on the shaft is what's different. I's close to a Remington, but the thumb piece is different than a Remington. It's close to a Springfield Armory Timber wolf, take down screw, but I'm not sure about that either! Good Luck!

Don't know but it took someone some time to make/finish it!

Craftsmanship...

That's what impressed me about it. It's not just a simple part.

A friend suggested a windage knob for a receiver sight....

Reminds me of the captive screw in a traditional Weaver scope ring.

Looks like a spring loaded screw that I have seen on a rifle that was used for a bolt stop. It screwed into the side of the receiver at the back of the bolt. To remove the bolt, you pulled on the head of the screw and the bolt would slide out of the receiver. I do not remember what rifle I saw that on.

Very close to the Remington model 12 takedown screw........ almost!

Similar design...

https://www.gunpartscorp.com/gun-manufacturer/remington/rifles-rem/12

Yessir....purt dang close!

I still cannot recollect anything about it, including how it may have ended up in my 'stuff'.

Looks like the "pre-cock" knob for a remington model 33 single shot 22