I am going to hang a METAL extension ladder using some METAL hooks. Now
that I have established some serious metal content, I need to drill the
mounting holes in the concrete garage wall. The hooks have 3 holes, and
I'm going to use plastic expansion anchors for the screws.

I have a nice Bosch hammer drill, but my past experience has demonstrated
very poor success at getting holes where I want them. The drill wanders
& bounces off pieces of agragate in the concrete, and I end up with holes
that won't match up with the holes in the bracket/fixture/whatever. I've
tried using a star drill as a centerpunch, but that only helps a little.

It seems to me that the absolute error gets worse with bigger drills, so
I can try starting small and then boring out the hole with a bigger bit.
Another option is to drill the first hole, and then use the hooks as a
jig to ensure that the subsequent holes line up. I was thinking about
using a small bit with a sleeve that fits in the holes in the metal hooks
to prevent the drill bit from chewing things up.

Any suggestions or tips from the experts out there?

Thanks!

Doug White