What gear should I buy to DIY mount a scope?

[NewsShooter]

String for making sure the scope is level and an allen wrench to tighten up the rings.

 

[TexasTightwad]

Yeah, but when you torque the rifle unnaturally because youre not comfortable its way worse that the tiny built in error.
https://www.snipershide.com/training-lesson-mechanics-rifle-cant/

The math is all sound, but I don't like to have built-in error. I would rather have error that can be corrected by training. That lesson kind of leaves one with the impression (probably unintentionally) that if you mount your scope canted to what's comfortable, you no longer have the potential to shoot with an unlevel scope. But no matter how you mount it, you should make sure you are level. So I look at it as an option between checking level and getting it right or checking level and getting it almost right.