Just finished installing the new Thorleys. What a job!!! I had one bolt on each side completely frozen. Had to drill which is why I am writing this. I had a few sets of really nice cobalt drills which hardly even touched these bolts. I struggled for a while and then decided to try something different. I tried carbide masonry bits and they worked great! Cut the metal like it was wood. From now on I will have a full set of these bits around and will not be shy in using them. Just wanted to let everyone know.