Shoulder thing that goes up

[carries an axe]

What are these things called?
Seriously, I need one.

[cyborg]

It's called "the shoulder thing that goes up".

[Solidsnake87]

Arg. I used to know what they are called. The point of the device was to make it easier on the shooters arms by placing the rifles weight on the shoulder. I know they were used on BARs during wwii. Try a search for "rifle shoulder support"?

[HardwoodRods]

I believe it's a butt plate shoulder rest

[sloppy joe]

M14 butt plate assembly (USGI)

[Cody]

That's obviously a barrel shroud.

[Blade Gunner]

Looks like a BDSM sex toy.

[carries an axe]

M14 butt plate assembly (USGI)

Awesome
Thanka

http://www.treelinem14.com/M14-M1A-USGI-Buttplate-Excellent-M14FBPEX.htm

[highpower790]

Entrenching tool!

[alpha_romeo_XV]

My M1A Scout has that butt plate, but I have never used it with the thingy up. I doubt it would be kosher using it flipped up in the off hand stage of a service rifle match.

[Tere_Hanges]

It rests on top of the shoulder to keep the butt from slipping down your chest.

If you have ever shot an M1A prone or an M1 or M1A in a service rifle competition you would know how slick the buttstocks are and how they can slip down easily.

[carries an axe]

I bought a spare butt stock for my vepr and I'm going to try and finagle it or something DIY on there.

[SonofWWIIDI]

Spatula for flipping pancakes/eggs/burgers in the field.

[86 5.0L]

Makes your rifle into a ghost gun that shoots 30cal clip magazines in half a second

[Cokebottle]

Clearly that is the aft bayonet.
Intended to be used when you are surrounded and out of ammo.