A countersunk, ribbed plug manufactured from PA6 nylon and fitted with a Zinc Plated or Grade 304 Stainless Steel drive screw. Suitable for use in Concrete, Brick, Concrete Blocks, & Natural Stone. Restricted use in Hollow bricks and blocks and Aerated Concrete Blocks. Hammer screws are suitable for use in most solid base materials ranging from reinforced concrete, concrete blocks, brickwork and natural stone. They can also be used in Aerated Concrete Blocks, but their load capacity will be limited by the strength of the block. Hammer screws can also be used in Hollow Base Materials but their use will be restricted by the thickness of the wall of the brick or block.