When agricultural experimenters send data to a statistics unit for analysis, they do not usually include a field plan of the experimental site unless specially requested to do so. But such a plan can be a great help to a biometrician: he can use it to check that the design used in the field was correctly described, and to arrange the plot residuals in the field layout as a way of detecting a fertility trend in the site and of relating anomalous values to particular locations on the ground. This paper gives examples of how a field plan can be used to the benefit of the experimenter.