Which tool is primarily used to apply and spread mortar when laying brick or block?

The tool primarily used to apply and spread mortar when laying brick or block is the trowel. A trowel features a flat, pointed blade that allows for easy manipulation of mortar, making it effective for both applying mortar to surfaces and spreading it evenly between bricks or blocks. This is crucial in masonry work, as the quality of the mortar application directly affects the strength and stability of the structure being built.

Each type of trowel can serve different purposes, such as pointing trowels for fine detailing or brick trowels for larger surfaces, but they all share the fundamental function of mortar application, which is essential when laying brick or block. The other tools mentioned, like the chalk line and bevel square, are important in masonry for layout and measurement tasks but do not serve the purpose of applying mortar. A masonry saw is used for cutting bricks or blocks, which, while an important part of the process, does not involve spreading mortar.