This is a pictograph of a hoofed animal's leg combined with two diagonal lines that resemble the Chinese character bā 八. Bā can mean all around or on all sides, which is the interpretation that I think applies here. Hence, Mahadevan's sign number 85 is an ideograph for the sound of reverberating hooves.
Illustrative Text Reference:
Harappa: Seal: H-447 a (NB. It is easier to see this symbol in image A): Sayid Ghulam Mustafa Shah and Asko Parpola, 1991: Corpus of Indus Seals and Inscriptions: Volume 2: Page 276: Collections in Pakistan: Suomalainen Tiedeakatemia.
Comments:
There is only one extant example of this Indus sign.
Inscription H-447 consists of one character. Therefore, my hypothesis is that it is an address.
The seal was found in a house in area F of Harappa. Mound F is associated with working platforms. Jonathan Kenoyer states that: "One of these circular platforms had what may have been a large wooden mortar placed in the center¹." A mortar would have made a pounding sound. Furthermore, the Harappa Archaeological Research Project reported that: "Initial results suggest that the platforms were not used for processing grain, but were more likely associated with processing something using water²." Water is used in the production of hoof glue. It is therefore possible that 'Pounding Hooves' was the address of the hoof glue factory.
Image Credit:
Indus Script Sign Number 85: Sign List of the Indus Script: Iravatham Mahadevan, 1977: The Indus Script: Texts, Concordance and Tables: The Director General Archaeological Survey of India.
Notes:
1. Jonathan Mark Kenoyer: Working Platforms, Harappa: Harappa.com: https://www.harappa.com/slide/working-platforms-harappa: Accessed: 26 June 2021.
2. Harappa Archaeological Research Project, 1999: Mound F, looking towards Mound AB: Harappa.com: https://www.harappa.com/indus2/157.html: Accessed: 26 June 2021.