Block bonding is similar in principle and practical methods to toothing but involves cutting out indentations into the end of the wall that are either three (minimum) or five (maximum) courses high. Using this method ensures that each indent achieves an optimum number of tie bricks. Block bonding is a little quicker and easier than toothing and tends to be used to extend unseen work, where adequate strength is still needed but the aesthetics of accurate or normal bonding are less important.
The depth of the indents cut into the existing wall will, again, depend on the existing bonding arrangement. For quarter-bond walls the depth of the indent will be 56mm and for stretcher bond, 112mm. When bonding in the new brickwork at the first course of each indent it is considered good practice to insert mesh reinforcement or wall ties, for additional strength at the junction between the new and old brickwork.