I'm having the same preblom as most people on the comment list. I have saved the linked files to a folder named add_mesh_walls' then copied that into blender/content/MacOS/2.64/scripts/addons. When I open up the user preferences window in Blender, I do see Add Mesh: Building Objects' and a checkbox to select it. So, I know I'm doing something right. However, I am unable to check the box which will enable me to use the Masonry addon. I'm not sure if I'm missing a technicality or something like that. I'm normally pretty quick as figuring this sort of thing out, but I'm stumped.I should add that when I saved the .py files, it originally had a .txt which looked like this Blocks.py.txt'. I took off the .txt extension for each file. Should I have kept those extensions attached when saving?