When the tear gas canisters were opened and the smoke billowed out, Hong Kong's demonstrators had only their umbrellas to protect themselves. They had been brought along because the heat of the sun was so severe at the height of the day.
Ever since then images and designs of umbrellas have been posted as a mark of solidarity. The "umbrella revolution" has become a protest art phenomenon online.
Along with a yellow ribbon, it has become an unofficial icon of Hong Kong's street protests.
When it rains...
Open your umbrellas, is the advice Hong Kong protesters have been spreading. The image of demonstrators in a cloud holding up their umbrellas against the pepper spray or tear gas moved many on social media to comment.
Over the last few years Hong Kong artist Kacey Wong has followed protest art as the people of Hong Kong began taking to the streets more often. On Monday morning, after a night which saw more tear gas and clashes, he issued a call-out on his Facebook page for artists to come up with designs for Hong Kong's #Umbrella revolution.
It was his belief that contemporary art is a clear platform for participation and advocacy and the designs poured in.
"I was inspired by seeing people defend themselves with domestic props. The contrast was so marked. On the one side there was police brutality and on the other side there were these poor umbrellas," Mr Wong told the BBC.
"The umbrella has been transformed from a normal every day object to a symbol of defiance, a symbol of resistance."
For him, the internet has liberated the movement beyond the streets of Hong Kong: "You don't have to be in a specific place at a specific time. Technology means so many more people can join in this protest."
Charlie Campbell of TIME shared this image of umbrellas on the streets of Hong Kong on Twitter.
And James Fallows in the Atlantic Monthly published a message from a reader in Hong Kong: "When we felt threatened, we opened umbrellas and raised our hands."
Tie a yellow ribbon...
Hong Kongers have taken up Tony Orlando and Dawn's song to Tie a Yellow Ribbon Round the Ole Oak Tree and on Facebook people have been changing their profile pictures to a yellow ribbon against a black background.
Instagram user natsushimo posted an image of a yellow ribbon tied around a banister at Hong Kong Baptist University. Students not attending the protest and working at school are also reported to be wearing yellow ribbons.
So many options to follow
Hong Kongers have an embarrassment of hashtags to follow for those interested in getting updates from the streets or expressing solidarity. #UmbrellaMovement is one hashtag that many believe will emerge as a leader.
But others inspiring people to comment are #yellowribbon. The Twitter account for the Chinese University of Hong Kong journalism course tweeted an image of a yellow ribbon being tied around a drone before it sets flight. #OccupyHK was also being used by demonstrators.
Dates have also proved popular #926 was trending and it had a tumblr and Facebook presence too - it refers to the date protests kicked off. Also making an appearance was #8964 - a reference to the Tiananmen Square crackdown of 4 June 1989 and also an expression of fear of some users about the situation on the streets of Hong Kong.