Abstract: A flat screen mesh element formed of metal or plastics material covers one or more core openings in a block of the next to topmost course in a foundation wall. When the topmost course of blocks is in place, mortar used to embed a foundation cap plate anchor bolt is placed in the core opening of a top course block which is in alignment with a locator tab carried by one end of the screen mesh element and extending beyond a surface of the foundation wall. The screen mesh element prevents the mortar from entering a core opening or openings of blocks below the topmost course. A large savings of mortar is achieved and the anchor bolts are installed at a uniform level on the foundation wall.