Trowel

The standard brick trowel has a diamond-shaped blade for scooping mortar off the board and spreading it into a bed joint in one motion, while a smaller pointing trowel handles tight repointing work and finishing details. Technique matters as much as the tool: how a mason angles the trowel to throw a bed joint, cuts off the excess, and butters a brick's end all affect how solid and void-free the finished joint ends up, which is something that shows up years later as a weak spot rather than right away.

A trowel gets used on every single piece of brick, block, or stone that goes into a wall, which is why an experienced mason can lay a much tighter, more consistent joint than someone still learning the motion. It's a hand-skill tool more than a power tool, and the difference between a fast, clean trowel hand and a slow, sloppy one is visible in the finished wall for as long as it stands.