A class of concatenated block codes, called generalized error-locating (GEL) codes, is proposed for error correction in digital magnetic storage systems. GEL codes are suited for high code rate applications with low-complexity (hard input) decoding algorithms. They offer high flexibility and can be adjusted to a variety of different situations. In this paper, we use as an example a (precoded) PR4 channel and consider GEL codes with BCH and Reed-Solomon component codes. Simulation results give bit error rates with and without constrained codes.