Also known as double expansionanchors,these expand from both sides for full contact and a securehold.Toinstall,tap into a drilled hole with a hammer and position yourfixture.Then,insert a screw or threaded rod andtighten.For maximumexpansion,the anchor should protrude slightly above the surface before threading thescrew.Pull-out strength and shear strength values are25%of the ultimatevalues.