Where do you apply a map with an apha channel on a V-Ray Mat

[KVMaster]

Can anyone explain how to use a VRay material, and apply a map with an alpha channel, to be used for cutting a hole out of the object the material is applied to.
With a MAX material you would just apply the same bitmap to the OPACITY channel and turn on the Image Alpha for the Alpha source.

But I don't know what channel to apply the alpha channel map too.

Can anyone give me some assistance. Thanks....

[RErender]

It goes into the refraction slot, set ior to 1 and in the bitmap controls, invert the output and set "RGB channel output" to "alpha as grey"