What surface to level gun on to install scope?

[hafejd30]

Level rifle level scope: Good

Canted rifle canted scope: Bad

Canted rifle level scope: Good!

Level rifle/level scope- zero canting- no exceptions for best results

[bearcatrp]

I use the wheeler kit. Works fairly well.
http://www.opticsplanet.com/wheeler-level-level-level-crosshair-alignment-113088.html