Gather your unwanted belongings and bring them to Mediamatic Fabriek. Register yourself and your things, and start looking around. If there was nothing that caught your eye, you received a voucher so you could come back and swap another time. It's like shopping, but without money.
What's cool is that you could keep track of what came into the exhibition, and what went out. The picture of your checked-in bow tie was connected at the check-out to a picture of the new well-ribboned owner. Take a look here.
You were also able to exchange services. The massage corner and hair salon were manned by professionals at fixed times, but when they weren't, you were free to take their place.