This chapter illustrates constructions of wiretap codes with examples from different types of physical channels. Coding criteria with respect to different types of channels are discussed, followed by explicit code constructions. Section 2.1 deals with the best understood example of explicit wiretap codes, referred to as wiretap II codes. They are built from classical error-correcting codes, and are used on a bounded erasure channel. Recent progress in the wiretap code design has been made thanks to the introduction of polar codes, which will be discussed in Section 2.2. Wiretap polar codes are best suited for symmetric channels. The approach presented in Section 2.3 is different from many points of view: first, it deals with additive white Gaussian noise channels (all the other cases considered are Discrete Memoryless Channels), and second, it approaches the notion of secrecy from a coding point of view, through an error probability computation. Wiretap lattice codes will be built.