What type of tiles features a coverlock and underlock?

Interlocking tiles are specifically designed with a coverlock and underlock mechanism, which allows them to fit together securely without the use of mortar. This unique system creates a watertight seal that enhances the roof's ability to shed water and resist wind uplift. The interlocking feature not only provides stability and durability but also simplifies the installation process, making these tiles a popular choice for both residential and commercial roofing.

Other options do not possess this specific locking mechanism. For example, flat tiles are installed in a more traditional manner without interlocking features, while cement tiles may have various designs but don't typically include a coverlock and underlock system. Glazed tiles are characterized primarily by their glossy finish rather than any specific interlocking capabilities. Thus, the defining characteristic of interlocking tiles makes them the correct answer to the question.