WTF are you trying to undo?

That's the slider, don't cut it.
On the back of the calliper there are two (7mm IIRC) allen key bolts, these are the bolt/slider (it's one piece) for the callipers. There is normally two end caps on, remove the end cap, undo the 7mm bolts and the calliper will come off.
The top slides out to the side then will lift straight off.
No idea what you're trying to undo as there aren't any carriers.......