Christmas tree anchor (saw sleeve anchor) is serrated metal expansion sleeve anchor. It has multiple sharp serrations on outer surface. Hammer it into pre-drilled hole, then drive the screw inside. The serrations bite firmly into porous substrate to prevent slipping. It is specially designed for aerated concrete, lightweight block, hollow brick. Material: carbon steel; finishes: yellow zinc plated, blue-white zinc plated. Widely used for fixing cabinets, railings, lamps in aerated concrete wall.