They also 'donated' used shoes to the embassy, saying the protest was in solidarity with Kulbhushan Jadhav's family.
The action was in reference to how Pakistan removed Jadhav's wife's shoes when she went to meet him, and never returned them.
There was "something metallic" in the shoes, Islamabad had claimed.
'Chappal Chor Pakistan' protests in Washington
The case of Kulbhushan Jadhav
Jadhav, a Mumbai native, is believed to be a R&AW agent. A Lieutenant Colonel in the Indian Navy, he is said to have sought retirement in 2013.
In March'16, Jadhav was arrested by Pakistan on charges of espionage and festering terrorism in Balochistan. He has been sentenced to death.
In December'17, Pakistan finally allowed a family meeting after India requested several times.
The mysterious case of Jadhav's wife's shoes
Afterwards, India slammed Pakistan for "harassing" his family and disregarding their "cultural and religious sensibilities".
His wife's shoes were seemingly of particular interest to Pakistan: she was made to remove them "for some inexplicable reason", India said. They were never returned.
Pakistan explained, "There was something in the shoe. It is being investigated. We gave her replacement shoes. All her jewellery etc were returned."
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'Incident has exposed Pakistan's narrow-minded mentality'
Protesters in Washington said they were against the "insensitive treatment" meted out to Jadhav's family in Islamabad.
"Pakistan ka matlab kya? Amreeka (America) se dollar la, Hindustan ke joote kha (sic)," one said.
Another said the incident had exposed Pakistan's "narrow-mindedness", and that "Pakistan as a whole is also being run by narrow-minded mentality".
The unique #JutaBhejoPakistan campaign
Earlier, BJP spokesperson Tajinder Bagga kickstarted a #JutaBhejoPakistan campaign. He tweeted a screenshot of his Amazon order: "Pakistan wants our slippers, Let's Give them Slippers. I have ordered Slippers & sent to Pakistan High Commission. I request everyone to Order 1 Pair Slipper for Pakistan."
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