How do I remove this rusty fastener under my sink?

[j7stin]

I don't now much about plumbing, but shouldn't this think be a little easier to remove? I added rust-dissolving solution, to no avail.

How do I remove this so I can change my faucet out? Is there a special tool or something? Can't get at it with a wrench. I also tried hammering it loose.

 

[Mr_David]

Drill it to split it.
Here is a picture of something similar.
Start with a smaller bit like maybe 1/4".
Then work it up to maybe 1/2"

Wear safety googles

 

[johnjh2o]

Use a basin wrench.