A shaped charge is also known as a hollow charge or a Munroe effect charge. It is an explosive device that has a conically or hemispherically shaped metal liner. When detonated, the charge collapses the liner, forming a high-velocity jet of metal that penetrates armor or other materials. Other synonyms for shaped charge include penetration charge, explosive lens, and self-forging fragment. A penetration charge is a type of shaped charge used to penetrate hard targets, such as tanks or bunkers. An explosive lens is a series of shaped charges arranged to produce a focused explosive effect, while a self-forging fragment is a projectile created by the explosion of a shaped charge.