Lag screws, also known as lag bolts, are used in wood construction for heavier load applications than most wood screws can support. We carry a wide selection in zinc and hot dip galvanized for exterior needs. We also stock lag shields. The Lag Shield is a screw style anchor designed for use with lag bolts. It is suitable for use in concrete and the mortar joints of block or brick walls. In harder masonry materials, short style Lag Shields are used to reduce drilling time. The long style version is used in soft or weak masonry to better develop strength.