Germany-based woodturner Olaf Schlieper has earned his living on the lathe for over 40 years. Custom table legs, staircase balusters and peppermills are his company's bread and butter.

When creating a new piece for a client, Schlieper turns the first one, then uses his lathe duplicator to crank out the requisite number of copies (orders of 20 table legs at a time are not uncommon). But while he's still got the original in the duplicator, he always has it make one or two extra copies, in case of defects.

If everything goes well, he has leftover units. Over time, these build up. Eventually they're used as firewood, to heat the shop.

Furniture designer Carsten in der Elst knows Schlieper, as Schlieper is the one who convinced Carsten to pursue design studies in the first place. Thus for Returned Objects, his final-year project at the Cologne University of Applied Sciences, Carsten asked Schlieper to collaborate. "The aim was to design something solely from [Schlieper's] already turned by-products," Carsten writes.

"The bespoke leftover table legs from various past productions have two things in common. They are more or less the same height and they have a square, unturned part that is usually building the corners of the table frame."

"Before the leftover table legs are glued into one block, the rectangular parts of the legs are flattened. We glue the legs into a nine-piece-blank. To prevent the unglued bottom side from splitting, a baseplate is screwed underneath."

"The danger here lays in imbalance of an asymmetrical fast turning object. Holding a tool onto this open and moving structure could end in serious injuries."

"Turning the piece to a cylindrical object, it took around 10 minutes on the lathe but more than 40 years of experience. Assessing the risk in this production is crucial and takes an open-minded craftsperson."