Readers tell how to keep concrete from staining swimming pool coping, how to make cleanup of finishing tools easier, how a half-round straightedge helps in meeting flatness tolerances, how sheet metal can be used to make column capital forms that save labor and how a simple tool made from metal conduit can keep wire mesh at the right location during slab construction. Other ideas cover precast concrete connections, reusable blockouts for forming wall openings and movable sleds that reduce crane handling time by holding wall form panels in a vertical position after stripping.