The Indus Dictionary Project
This is a pictograph of someone holding a noose. The noose is the key identifier for this Indus sign. Therefore, Mahadevan's sign number 31 is the noun catcher.
Harappa: Seal: H-94 a: Jagat Pati Joshi and Asko Parpola, 1987: Corpus of Indus Seals and Inscriptions: Volume 1: Page 189: Collections in India: Suomalainen Tiedeakatemia.
I rather like seal H-94 because it appears to tell us how to capture a tiger. The motif incorporates a basin, which I take to be a water bowl. Hence, my interpretation is that the tiger would be caught when he went to drink.
Indus Script Sign Number 31: Sign List of the Indus Script: Iravatham Mahadevan, 1977: The Indus Script: Texts, Concordance and Tables: The Director General Archaeological Survey of India.