Rock grouting tends to be used to fill fissures in the rock, reducing the amount of water that filters through the rock mass. It is usually carried out with a single packer that is inserted into the previously drilled bore to the pre-established level; grouting is carried out and then the packer is raised by stages, normally every 5m, until grouting of the bore is complete. Grouting has traditionally been carried out with cement-bentonite mixes, and occasionally micro cement is used.