For the rough-cutting of bricks for unseen work, it is possible to use the cutting edge of the brick trowel, simply holding the brick in the laying hand, estimating by eye the length of the cut brick required and giving a sharp blow with the cutting edge of the trowel to remove the excess. However, this method is not recommended and, over time, it will shorten the life of the trowel, particularly when it used on harder engineering bricks. It is much better to use a brick hammer that has been designed for rough-cutting and can provide a greater degree of ease and accuracy.
When rough-cutting bricks, try to cultivate a good eye for brick length. It can help to offer up the brick to be cut to the gap where it is intended to fit, and mark it with the blade of the brick hammer,
not forgetting to make an allowance for cross-joints at both ends.