The linker is a set of computer procedures that combines agricultural economic country models into a world system that can be used for scenario analyses. The models generally have exogenous macroeconomic and resource blocks but have endogenous prices, quantities, and policy behavior for grains, oilseeds and products, and animal products. Most of the models are spreadsheet-based, with the exception of the U.S. and rest-of-world models, which are based in the Fortran programming language. The linker combines the models even though they reside in disparate software packages, appropriate to the needs of the respective analysts. Software has been selected or internally developed with the goal of facilitating' input of expertise from country/regional, commodity, and other analysts. The combined country models and the linker are referred to as the Country Linked System (CLS). The CLS is being used to perform middle-run scenario analysis in the Market and Trade Economics Division. The linker is not the best answer to combining the models, because it is large and slow. Instead, the linker is a functioning platform on which to work out input needs, efficient processes, and desired output. We can evaluate other modeling and solution software packages on their ability to meet or exceed the capabilities of the CLS. In the meantime, the CLS makes possible a number of scenario analysis projects. This report describes how to locate and interpret the output, how to set up the linker's control files, and how to run the linker and deal with typical problems.