When used, it is often necessary to resize bricks. This operation can be done in two ways.
First of all, measure and draw a bold pencil line on the four faces of the cut brick.
Use a cut-off grinder
First possibility: for a clean cut, use an angle grinder equipped with a cutting disc masonry.
Use a chisel
Second possibility: for a faster cut, but without a particular finish, cut the brick with a bricklayer's chisel and a mallet.