Pick Brush

To use a brush, left-click on it.

The Single brush place blocks from a long distance. To place a block, ensure it is in your hand(only if you disabled the Brush mode, and set the Origin to Face, otherwise, use the Nether Star), this specific brush is redundant if you have Axiom, and if you kept Brush mode and Origin in their default values you won't notice a change, so you might want to skip to the next brush.