The meat, juice, jars, lids, and rings are all packed hot and go into the hot pressure canner with the correct amount of water in the bottom. The cover will be secured on top and the canner will be brought up to steam. The weight will be added later according to the directions which came with your canner, and then the whole unit will be brought up to the pressure specified in the meat canning recipe you are using, and kept at that pressure continually. The MIRRO brand canner weight I am using today has three holes allowing you to select 5, 10 or 15 pounds of pressure by fitting the correct hole over the stem on top of the canner lid. Some canners have a gauge you read instead.