A door closer hidden in the door frame and in the door-leaf is a device which, after the door has been opened and left open, makes the door-leaf shut on its own. This system uses adjustable hydraulic valves which close the concealed PIU door in two stages. Initially, the door closes fairly fast only to slow down just before closing completely to avoid a violent collision between the door-leaf and the hidden door frame. The door-leaf is gently pulled towards the door frame.

Both stages of the door closing action can be separately and conveniently adjusted, i.e. it can be made faster or slower as wished. In addition, the door-leaf is equipped with an angle limiter (up to 120°). It is a hinge restrictor which protects the door-leaf from being pulled out or prevents it from opening too far and damaging the adjacent wall or other items. It is possible to adjust the closing strength of the door-leaf (force 2-4 according to EN1154), which is especially important in the case of door-leaves with glass panels.