A user's manual was developed for the W-line numerical sediment transport model by the Coastal Engineering Research Center (CERC). This report provides the necessary guidance, complete with multiple example applications which include model input and output, for using the N-line numerical model. Capabilities of the model include the simulation of (a) single or multiple shore-perpendicular structures, (b) single or multiple detached offshore breakwaters, and (c) disposal of material or dredging of material in the coastal zone. Model parameters are discussed in order to guide the potential user to a successful application of the model. The N-line model is versatile, easy to use, and capable of producing dependable results when used for appropriate applications. The documentation presented in this manual is intended to cover only the breakwater subroutine, Since conceptual modifications were not made to the original model, the original documentation, presented in CERC's report MR 83-10, should be obtained by any potential user of the model. The N-line model is useful in showing qualitative trends for a complex case such as Lakeview Park, Lorain, Ohio. Some of the drawbacks of the program when modeling Lakeview Park, such as the inability to reach an equilibrium shoreline, and the low sinuosity of the shoreline when influenced by breakwater segments, could possibly be successfully modeled by modifying the different input parameters, such as the ADEAN parameter and/or initial shoreline location and/or the model code. Perhaps then a quantitative verification of the model could be made. However, in this case, the model would have then been tailored to produce a previously known result. A project cannot be successfully modeled without experimenting with different timesteps, space-steps, contour depths, shoreline locations, and structure configurations, A wave climate representative of the area being modeled is also very important. Finally, the response of the model to a particular setup must be interpreted with engineering judgment.