EXPANSION ANCHORS ARE TYPICALLY REQUIRED TO JOIN OBJECTS IN CONCRETE OR MASONRY. THESE BOLTS CONSIST OF A STEEL CASING WITH FINS AT ONE END, AND A STANDARD SCREW INSERTED IN THE CENTER OF THE CASING. INSTALLERS START BY DRILLING A HOLE, THEN INSERT THE BOLT BY HAND. ONCE THE BOLT IS IN PLACE, A SCREWDRIVER OR DRILL IS USED TO TIGHTEN THE SCREW. THIS PULLS THE SCREW UP INSIDE THE FINS OF THE BOLT, FORCING THESE FINS OUT TO THE SIDES.
USERS SHOULD KEEP IN MIND THAT AN EXPANSION ANCHOR IS ONLY AS STRONG AS THE MATERIAL IN WHICH IT IS INSTALLED. THIS MEANS THAT AN EXPANSION ANCHOR WILL NOT HOLD IF THE SURROUNDING SURFACE IS WEAK OR BADLY DAMAGED. EXPANSION ANCHORS MAY NOT BE SUITATLE FOR USE IN DAMAGED OR CRUMBLING CONCRETE OR SOFTER WOODS.