Quote Originally Posted by Klainmeister View Post
I'd recommend using a needle instead of a knife. Sand down the location till it's as thin as possible, and gently use the needle to create a holet.
But how to check that the hole is round and with a nice clean edge ?

For that, pop it on a glass carrier inserted in to an enlarger - With the column racked up high, focus a nice sharp image on the baseboard. You might be surprised at how rough the hole is.