Tamper-resistant or security fasteners are often used to prevent unauthorized entry. They are often non-removable or require a special tool to remove them. Higher-quality tamper-proof fasteners have hardened heads, making it difficult to form a new drive slot with a file.
A major cause of failures in metal fasteners is electrochemical corrosion (rust), or so-called galvanic action. Engineers and designers alike can greatly reduce this type of corrosion by specifying fasteners made of the proper materials or with the right coatings....More
Bolts and screws can be outfitted with a variety of different head styles. Which style an engineer specifies depends on several factors: the type of driving or installation equipment used, the type of joint load, and the external appearance desired.