How to Repair Mortar in a Brick Wall

Scoop a dollop of mortar onto a brick trowel or hawk, hold it up even with a bed joint, and push the mortar against the back of the joint with the tuck-pointing trowel. Eliminate voids with a few slicing passes of the trowel's edge, then add more mortar until the joint is filled. Once you've finished three or four courses of bed joints, go back and fill the head joints. Finally, smooth and compact all the mortar with the trowel's flat face and scrape the excess mortar off the brick.