Epoxy putty is a room-temperature-hardening substance used as a space-filling adhesive. It is stored until use as two components of clay-like consistency. Kneading the two components into each other creates an exothermic chemical reaction that activates the substance for use by catalyzing an epoxide polymerisation reaction. Unlike many other types of glues, an epoxy adhesive can fill gaps and even be molded into a structural part. Some makers claim in advertising that one can drill and tap their cured product, and that it quickly cures “hard as steel” (as measured by Shore rating), though it is much weaker than steel in tensile strength and shear strength.