Before using the string, apply powder to the area you want to mark. Then pull the string along the marking. It should be stretched between two opposite points on the wall. Lay bricks close together along the string. Do not mortar the joints between them. For perimeter walls, start by laying the corners. Ensure each corner brick is oriented at 90° to the others. It is recommended to wear a mask and gloves when working with this powder, as it contains hazardous silicone dioxide. If inhaled or comes into contact with skin, rinse the affected area immediately for 15 minutes. If irritation persists, seek medical attention immediately.