Manipulators of Rounding with Constant Radius

Radius manipulators have a shape of a blend surface's cross-section (arc) with two square markers at endpoints.

On straight edge a single manipulator appears at the midpoint. On curved open edges two manipulators split blend surface in equal length sections. On curved closed edges either two or four manipulators might appear in different cases.

Moving the mouse cursor over any of a manipulator's endpoint markers leads to a radius icon appearing near the cursor. Dragging the mouse while holding, when the radius icon is present, leads to blend Radius value change in accordance with the cursor movement. Depending on the Common Properties checkbox condition, Radius changes either for all edges at once (which affects the appearance of their manipulators) or for the corresponding edge only. Both endpoint markers of a single manipulator work in the same way - it doesn't matter which one to use.