The Indus Dictionary Project
This is a pictograph of an adult person, with the addition of a bar across each leg. The bars may depict wooden legcuffs. The leg area can give us information about the status of a person. In this instance, we can see that the leg restraints would make movement extremely difficult. Hence, it can be inferred that this is the noun prisoner.
Harappa: Seal: H-477 A (NB. There is no view a for this inscription): Sayid Ghulam Mustafa Shah and Asko Parpola, 1991: Corpus of Indus Seals and Inscriptions: Volume 2: Page 281: Collections in Pakistan: Suomalainen Tiedeakatemia.
There is only one extant example of this Indus sign. In inscription H-477, the word prisoner follows the noun place. This gives us a place for prisoners, in other words a prison.
Prisoner: Lynn Fawcett, 2017.