Corner bead is usually applied in places where you have solid lumber backing. I'd try this first to hang your hardware without anchors, which usually aren't intended to be used in wood:
- Mark the location of your screw holes.
- Find a drill bit that's just larger than the outer diameter (threads) of the screws you're using. Carefully drill just through the corner bead at all screw locations. It may be helpful to pilot with a smaller bit to prevent "walking" of the bit as you begin.
- Find another drill bit the size of the screw shank or slightly smaller. Pilot about an inch into the lumber.
- Mount your hardware. Do not overtighten, as you'll crack the drywall mud overlaying the bead and deform the bead.
If you find that your screws aren't long enough to get through 5/8 to 3/4" of drywall and bead plus enough wood to securely hold, stop by the hardware store and pick up longer ones. This is the right way to do this job, but you don't want your screws to tear out under load. Try to get at least 3/4" into the lumber.
If you find that you actually don't have lumber backing, you'll need to drill holes in the bead the size that the anchors call for. This can be quite large, and you run the risk that the bit catches the sheet metal and tears things loose. I don't recommend this approach. If you must do it, drill through a block of wood first, then hold it firmly over the bead as you drill through it. This should help prevent most damage. Again, don't overtighten the screws.
