How to get several people to sit on the sofa

It only takes one person to sit on the sofa to make others feel that it is taken. This can be a problem, for example, in entrances and corridors where there is limited space for seating furniture but where many people gather to wait for visitors or transport services. Putting a middle armrest on the sofa makes it natural to sit on it even if someone is already sitting there. The seats can be used by more people and the space can be used more effectively.