Because a single verse offers two admissible terminations, the form is also described as tawshīḥ or dhū al-qāfiyatayn—a verse with two rhyme endings.
The extension must not be unrelated verbal decoration. It ordinarily develops or completes the existing rhetorical intention, so that the two readings remain connected.
To recognize the device, mark both stopping points and test the meaning and metre of each. These alternative names refer here to the same formal practice, not three distinct ornaments.