The BMGTools, created by IFREMER, are a set of pre-processing tools that help you create, check and modify bathymetric grids. CheckBMG is a part of the BMGTools. Its purpose is to help you to visualise grids created with the MARS code or with other applications and to allow you to check the relevance of the interpolation. If necessary, you can modify the grid to manually correct algorithm errors. The present document is the user manual of CheckBMG.