Stockholm designer Thomas Bernstrand has created an outdoor stool that locks up like a supermarket trolley to keep parks and public spaces tidy.

The stool is the latest in the designer's Share series of street furniture for outdoor brand Nola. He has previously designed a chair and a wheelable lounger.

Unveiled at Stockholm Furniture Fair, the stool is designed as an alternative to fixed public seating, aimed at city dwellers who want to carry it to their chosen spot in the sun.

"Some people like to sit alone under a tree, others like to sit in the sun and others like to sit together," Bernstrand told Dezeen. "People have so many different needs, so a loose chair in the park is a great feature."

Similar to airport and supermarket trolleys, each stool has an attached chain and coin-operated mechanism that lets them be locked together. Rather than deterring would-be thieves, the addition is more about making sure park visitors tidy up behind themselves.

"One euro is nothing for a chair like this," explained the designer. "The coin is there so all the chairs find themselves back at the station, so the next user can find them easily. If the chairs are left all over the park it will be difficult to cut the grass."

The Share stools are made in metal, which was chosen for its durability and weight, to stop the seats flying away in the wind. They stack vertically to form a column, and are intended for use across in squares and shopping centres as well as parks.

Bernstrand unveiled the stools at Stockholm Furniture Fair, which took place from 7 to 11 February 2017, and where Bernstrand also debuted an award-winning segmented modular sofa, designed in partnership with Stefan Borselius.

Photography is by Jann Lipka