Boeing’s 747 has more than 6 million parts, and about half of those are fasteners. Because of the many fasteners used, replacing mechanical fasteners with adhesives can substantially reduce the weight of aircrafts. In aerospace applications, adhesives help performance and durability by distributing stress evenly across a bond. This is in contrast to bolts and spot welds, which concentrate stress on a smaller point. Adhesives are also important for laminating dissimilar surfaces such as metallic and composite substrates. In some cases, aerospace adhesives can have shear strength comparable to mechanical fasteners, making them viable alternatives to mechanical fasteners. In addition, adhesives can maintain surface integrity by protecting materials from wear and corrosion, and by maintain a smooth, uniform surface and line the holes required for fasteners and the projections created by bolt heads. Overall, use of adhesives can offer improved performance with reduced weight.