There are many models of Ultra-Drain Guard. And most of them are held in place by the weight of the storm drain grating. The one exception to this is the Adjustable Model. Instead, this unit relies on a steel framework to keep it from falling into the basin.
The steel framework adjusts to fit different sized drains.
What is the advantage of this type of installation? For one thing, the Drain Guard remains in place even when the grating is lifted. With other models, crews need the foresight to secure the Drain Guard before lifting the grate. The other advantage is aesthetics. There is no excess material to trim or that may stick out above the grating. It's a clean and simple installation.