Abstract: The present invention is concerned with a device for tensioning a chain. The chain tensioner in accordance with the present invention was developed in particular for securing deck cargo on ships and for binding timber bundles. As regards its technology, it is simplified as extensively as possible in order to reach reliability of operation in all possible circumstances. Owing to the simplicity of the construction, almost all maintenance becomes unnecessary and a reliability of operation is reached that meets the requirements imposed by the recommendations of the IMCO (Intergov. Maritime Consultative Organization).