Can anyone tell me how to turn off this unusual toilet shut off valve

[budgieselena]

I tried turning the rectangular metal thing on the end either right or left with my hand but it does not yield to gentle pressure just seems stuck where it is.

 

[Snoonyb]

Welcome.
That's a typical 1/4 turn angle stop and the handle is the lever, and off should be a 1/4 clockwise rotation.
You can slightly rotate the nut behind the lever, counter-clockwise.

 

[budgieselena]

thanks a bunch

 

[mikejurasw]

Put a rag under it, hit it with PB blaster, then (gently) throw a crescent wrench on the lever.