Repointing brick, stone or block involves removing the mortar between the masonry units and replacing it with new mortar.  As discussed in the previous post it is essential to match the mortar to the type of masonry wall and to the masonry unit used.  Mortar should be removed to a minimum depth of 1 inch or 25mm.  All loose, deteriorated mortar should be removed until you hit sound mortar.  Joints should be cut back as square as possible to assist with the mechanical bond of the mortar. Deep voids should be back pointed first.  Back pointing is refilling the mortar in the joint up to 1 inch or 25mm back from the face of the unit.  Once the back pointing mortar is set you can front point.  Front pointing  means to fill the joint up to the face of the stone.  This multistage process ensures the mortar has time to set more evenly which helps avoid cracking of the joint and helps keep mortar color consistent.