Patio doors are designed to achieve a compromise between easy to open and close (which requires little contact between the moving door leaf and the outer frame) and being good at keeping out the wind and the rain (which requires a good seal between the moving door leaf and the outer frame).
The majority of patio doors are opened by pushing the door leaf to the side. When doors are of moderate size and weight this ‘slide’ mechanism allows the doors to be opened easily enough.
For the bigger doors (it is possible to have door leafs that are up to 3m high and weigh up to 400kg) it is advisable to opt for a lift-and-slide mechanism. Turn the (slightly longer) handle through 180° and the door leaf is lifted by a few millimeters to reduce the friction between door and frame. This makes it possible to move even the biggest and heaviest doors with relative ease.