We recently remodeled our kitchen and installed a counter height pass-thru window above the sink. We installed SileStone brand quartz countertops inside and ask the stone contractor to fabricate a shelf to install outside the window, the window measures 53" horizontally, and the shelf is 59" by 12". Our walls are concrete and block. The window is framed in concrete and has a very small "ledge" 2.5 inches. We are wondering now how to install this shelf, since it is quite heavy (about 100 lbs) and we want to use it to put drinks and trays of food when we have a party, also, people will tend to lean on it and add more weight. Should we use brackets screwed to the outside wall, or is there a kind of bracket that can be embedded inside the wall and stuccoed invisible? Please advise. Thank you.