The Indus Dictionary Project
This symbol is the outline of a boat. It shares a common root with the Chinese character zhōu 舟. Therefore, it is the noun boat.
Harappa: Tablet in bas-relief: H-1840 B: Asko Parpola, B. M. Pande, and Petteri Koskikallio, 2010: Corpus of Indus Seals and Inscriptions: Volume 3,1: Page 258: New material, untraced objects, and collections outside India and Pakistan: Suomalainen Tiedeakatemia.
The number of compartments may give the size of the boat in Indus units.
Inscription 1840 is interesting because the boat is accompanied by a pictograph of a cormorant drying its wings. This is normal behaviour for a cormorant that has been fishing. Hence, it is an ideograph which tells us that fishing has finished for the day.
The tablet was probably a permit for the sale of fish in Harappa.
Boat: Lynn Fawcett, 2018.