Yup.
That would be a
tangent sight, aka
elevator sight. They often have vernier scales for elevation.
Contrast that with
tang sights, which mount on the receiver
tang, near the wrist. You can have a tang-mounted tangent sight, like my 1874 Sharps Business Rifle, just to make things more confusing. Tangent sights don't always mount on the tang, though. Many are found mounted on the barrel just in front of the receiver. An example would be the rear ladder/tangent as found on my 1903A1 Springfield.
The Nerf will need a lot of tangent sight elevation to score hits way out there with those foam dart trajectories.
I wonder if the belts can be made longer, and slung over one's shoulder or arm, ala' Rambo?