I have seen buildings with a horizontal projecting band of brick masonry in a rounded bullnose shape. These typically have closely spaced vertical joints. The brick wedges that form the outside corners of these bullnose bands appear to be held in place only by mortar. What keeps these brick wedges in place?
The outside corners on bullnose brick belt courses often are made of special larger corner sections with false joints. The false joints are then filled with mortar to look like any other mortar joints. Prefabricating these corner sections out of smaller units also is possible. In this case, the wedge bricks in the corner should be reinforced or otherwise tied to the rest of the assembly so that they won't loosen and fall out with age. This can be accomplished by drilling holes in the corner wedges and tying them back to the assembly with stainless steel wire.