Scru-Leadâ„¢ Wall Anchor Print The Scru-Lead anchor is designed for use with sheet metal or wood screws in concrete, block or brick. The anchor is made entirely of lead alloy which is soft enough for easy installation, yet hard enough to give secure holding power. The performance of this product depends on the integrity of the base material. These fasteners are not recommended for use overhead or applications where holding values are critical. Read Less