Notched trowels are metering devices. Notch size and configuration allow a specific amount of mortar to be applied to the substrate. When a consistent trowel technique is used, the amount of mortar for the bond coat remains consistent. This, along with proper installation methods, will help ensure proper coverage and limit lippage between tiles. Trowel selection should be based on tile size. Typically, as the size of the tile increases, the size of the notch must increase. Never assume a certain trowel notch size will guarantee good coverage, always check coverage periodically during installation.