Much like coin-based cart systems found in supermarkets and airports, these stackable stools (which double as table surfaces) can be borrowed, moved around and returned with ease. Unlike fixed-position urban benches and tables, this design by Thomas Bernstrand lets users control their own experience, setting up a solo seat or group of seats and surfaces in the sun or shade as desired.

While not foolproof, of course (anyone intent on stealing them or leaving them out could do so), the furnishings do demand a small deposit to encourage people to to put them back when they are done. Also, the dangling chain and branded mark could help deter their disappearance into people’s homes.

In the United States, where the maximum value of an everyday-use coin is fairly small, the incentive would be correspondingly diminished. But in Euro countries where denominations are typically higher, the price of failing to return the items would be significantly higher.

The metal stools are made to be heavy and durable, keeping them from being knocked over in the wind and making them suitable to frequent outdoor use. They also stack neatly into columns, taking up less space on the streets (or in shopping centers or parks or squares) when not in use.

The designs are an extension of the Share Series, a set of seats and other objects with similar coin-operated functionality intended for public use.

Other pay-to-sit urban furniture projects include a chair series by Vincent Wittenberg, a bit more comfortable looking but they also take up more space on sidewalks.

Also: Fabian Brunsing, a Berlin-based artist and designer, took a different approach the problem (a bit more tongue-in-cheek). His bench uses coin deposits (but in this case non-refundable) that allow you to use a public bench. But when your time runs out: stand up fast to avoid the spikes.

The privatization of public spaces is a contentious issue – suburban malls have turned many main streets into ghost towns. At the same time, there are legitimate difficulties when it comes to open seating . If you leave benches wide open, people may sleep in them. If you don’t nail chairs to the sidewalk, people will walk off with them.

Consider shopping carts: in the United States, you see them strewn around parking lots, or gathered by tireless employees. In many parts of the world, including Europe, a coin is inserted, allowing you to detach the card, but encouraging you to return it and get back the money you put in. Could the same system be used for seats? Vincent Wittenberg gained permission from Bat Yam, Israel, to perform a real-world test.

“We proposed to the municipality to replace existing public benches with benches that consist of individual seats. The bench itself is a docking station: using a five Shekel coin one can release a seat and place it in a different spot. The deposit is returned when one brings the seat back. The chairs introduced by the municipality cross the border between public and private and move between the sunny sidewalks to the shadow under the arcades.”

Meanwhile, Fabian Brunsing, a Berlin-based artist and designer, took a different approach to a related problem: coin deposits (but in this case non-refundable) that allow you to use a public bench. But beware: when your time is up, a warning sound signals you should stand or get spiked from below. Perhaps this project takes things too far, but, on the other hand, is it that different from toll roads and other pay-to-use amenities offered by cities or states?