New Yorkers rely on the subway everyday, yet an item as commonplace as the MetroCard still holds many surprises. For example, you’ve likely noticed that our beloved transit cards have slanted edges and tiny holes, but what’s the explanation behind these seemingly arbitrary design features? We did some digging on behalf of curious commuters everywhere:

The MetroCard first arrived to the New York City subway scene in the early 1990s, serving as a modern replacement for subway tokens after they were discontinued in 2003. Considered to be revolutionary for its time, it allowed New Yorkers to navigate in and out of the subway without having to lug around heavy pocketfuls of change. In the years since its arrival, the flimsy fare card has undergone various iterations in design: the first version was actually blue, and collections of temporary special edition cards have been released. The hole and slanted edge, however, have stayed consistent.

According to MTA spokesman, Shams Tarek, it’s actually “used by the internal mechanism of fareboxes on buses for alignment and timing purposes as the card is pulled in and pushed back out.” In a Quora forum, MTA Bus Operator, Jonathan Perez, expands on this, noting that each MetroCard slot in buses has a rubber grip and pin that goes in the hole to swipe the card up and down. “The hole is also to ensure the card is facing the right direction as the hole is offset to one side,” he says.

Additionally, the slanted edge was added to accommodate all riders, helping them easily identify what side of the card to insert or swipe first. Tarek explains further, “The slanted corner is to help the visually impaired swipe or dip the card in the proper orientation. Obviously this helps anyone use the card without looking if needed.”

For more history on the world’s largest rapid transit system (in area), make sure to join us for our Underground Tour of the NYC Subway, where we will be weaving in and out of past and present stations:

Underground Tour of the NYC Subway

Next, check out the Top 10 Secrets of the NYC Subway and 11 Vintage Subway Amenities the MTA Should Bring Back.