Laminated glass is a type of safety glass that holds together when shattered. In the event of breaking, it is held in place by an interlayer, typically of polyvinyl butyral (PVB), between its two or more layers of glass. The interlayer keeps the layers of glass bonded even when broken, and its high strength prevents the glass from breaking up into large sharp pieces. This produces a characteristic "spider web" cracking pattern when the impact is not enough to completely pierce the glass. Laminated glass offers greater protection for people and property by providing an effective barrier from attack. Although the glass will break if hit with a hammer, brick or similar object, the interlayer can resist penetration, ensuring any attempt to enter a premises will be slow and noisy. Process PVB laminated glass is manufactured by combining two or more annealed or heat treated glass sheets bonded with one or more of PVB interlayer's and subjected to heat and pressure, in order to ensure perfect adhesion between the constituent elements.