I’ve been weary of screwing and nailing into CEB blocks for a long time, but have had no good evidence to support my worries. I was pretty surprised by how well they grip the block and am not as worried about hurting them as I used to. I was able to lift the block using two screws which means they were each holding around 15 pounds. I am still a bit weary of attaching anything very heavy like shelves, cabinets or counter tops to them, but I’m thinking that hanging mirrors, pictures, etc should be fine. More experimenting to come. Any experiments you would like me to try?