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Before determining what is good and bad for a particular mechanism for sliding doors, it is advisable to conduct a brief overview of its most common types. Most doors use only three design principles: sliding, swinging open and folding.
Of these three, swing doors are the most popular. They historically appeared earlier than others and have a design familiar to everyone: the door is fixed in the opening with hinges and can move in one of two directions. This design has a significant drawback: when open, the door occupies a fairly large area.
Folding doors are used relatively rarely. Sliding door mechanisms of this type involve the movement of several panels with the help of springs, allowing the structure to fold quite compactly. You can observe this type of door in public transport. The disadvantages of this type of construction include a small degree of sound insulation.
Sliding door design
The construction set of mechanisms for sliding doors, in addition to the door panels, also contains a number of parts necessary for assembly. Here is a list of the standard delivery items:
- door panels;
- Box;
- Guide elements;
- Fittings;
- Cassette.
The listed parts are included in the standard minimum, so even the absence of one of them may make assembly impossible.
door panels
The number of panels for a sliding door can range from one to eight. Any door can be used as a door panel, except for doors with a non-standard profile, such as, for example, arched doors.
Single sheet system. door frame
Despite its name, the door frame is U-shaped. This structural element is placed in the opening, and panels are mounted directly on it using the mechanisms of sliding interior doors. The process of mounting the box is carried out using screws or adhesives.
Most often, the door frame is completed with decorative elements, the only function of which is to enhance the aesthetic qualities of the door.
rail mechanism
The rail mechanism is the part that performs all the functionality of the sliding door mechanism, so the installation process of this element should be taken with all responsibility.
To limit the possible gap of movement of the door, two limiters are provided, one of which is attached from below, and the second from above.
The number of rollers that ensure the sliding of the door along the guide rails should depend on the mass of the door leaf: the greater the mass, the more rollers. 
The rail mechanism is a rather complex structure, so choosing it yourself is not recommended. The best solution would be to purchase this roller mechanism complete with sliding door panels.
accessories
For the most part, a variety of door handles belong to this class of parts. But in the case of sliding doors, the handles must have a special shape that minimizes the protrusion of the handle beyond the surface of the door leaf. This design allows you to hide the sliding mechanisms in the door cassette.
The standard set of mechanism for sliding interior doors already includes such a handle, but if necessary, you can choose and mount the appropriate fittings yourself. 
Sliding door fittings also include cylindrical elements that allow the door panel to move with a light touch of the fingers.
Cassette
This structural element may not be included in the standard configuration of the sliding door. Its principle can be illustrated by the example of a video cassette: if we imagine that the door leaf is a video cassette, then the cassette is a box in which the video cassette fits compactly.
The key to quiet and smooth operation of sliding interior doors is high-quality fittings. Roller structures have a complex structure and require the use of an extended set of elements.
The set includes:
- guides. As a rule, modern door systems are hinged. Large and heavy sliding doors are often equipped with a floor rail. Guides are made of steel and aluminum;
- rollers equipped with bearings. Elements often have a rubberized shell for softness of movement;
- accessories for rotary models. The functioning of these original products provides a rotary mechanism;
- pencil cases. Metal structures are built into the wall, only the sash remains in sight;
- special handles.
The main criterion is the weight of the wings. For heavy sliding doors made of solid wood or glass, it is better to purchase reinforced rollers. Also pay attention to the following nuances:
- the rail should be twice as long as the interior canvas;
- the floor track should ideally have a seal that prevents clogging;
- aluminum profile is quieter than steel;
- the number of accessories is selected based on the size and number of sections.
You can personally evaluate the entire range in the showroom in Moscow.
Traditional swing doors are not always a good solution. When opening for such a model, you need to leave a fairly decent area unoccupied. But sliding doors on rails and rollers do not take up space at all when opened.
Sliding folding door mechanism
Sliding system mechanism
There are several options for interior doors of this kind, but the principle of movement remains largely the same. Its essence is to provide not opening, but displacement of the sash along the wall or the second sash. At the same time, the area near the doorway remains free, and the doorway remains open.
Sliding door bottom rail
To achieve this effect, use a special mechanism. Along the movement of the door leaf on the floor, wall or ceiling, a special type of profile is fixed - guides or rails. Rollers are installed on the door itself. When opening, the rollers move along the guide, and the sash moves to the side.
Sliding doors with glass inserts
There are 2 types of such a system.
- Floor - the door leaf is inserted into two guides - upper and lower. The main rollers in the lower part of the web provide movement along the lower guide, the upper rollers move along the upper rail, holding the web in a strictly vertical position. This option is very reliable and durable.
- The suspension system assumes the absence of a lower guide. In this case, the rollers are fixed only in the upper part of the product. When opened, the rollers move along the top rail, providing both movement and vertical hold. The option is more effective and more suitable for interior doors: the lower guide forms an unpleasant threshold, and in this case it is absent.
Hanging sliding door system
However, the suspension system requires reinforced fittings, so it is not suitable for doors made of heavy materials - solid wood, glass, for example. In the photo - doors on rails in Leroy Merlin.
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Varieties of interior doors
In Russia, a solution of this kind is extremely popular, so you can find products that are optimal in terms of cost and quality not only in specialized stores, but also in large hypermarkets, for example, Leroy Merlin. There are always several dozen different models in the catalog.
Accordion doors in Leroy Merlin
But before choosing a product by color or shape, you need to decide on the type of interior door and the principle of opening, and they are different.
- Sliding doors - 1 or 2, the most famous option in Russia. This is a classic model - hanging or floor, performed in all possible styles. Guides can be installed both on the wall and on the opening or even on the ceiling, and the material used for manufacturing is very different - from chipboard to glass.
Sliding interior doors differ from the sliding wardrobe option by the principle of convergence.
The sashes do not go one after the other, but are joined in the center of the doorway, so that only one rail is fixed on the floor.
- Cassette - the sash moves according to the same principle, but it does not move along the wall, but inside it. More often, this does not mean a recess in the main wall, but a false panel that is mounted on the outside of the wall. The solution looks very elegant. Doors can be either single or double doors.
- Folding - the mechanism of interior doors on rails and rollers of this kind is different. When opening, the sash folds at least twice, and then shifts to the side of the opening. In this case, it blocks part of the opening, but practically does not occupy the area of the room. The rollers are fixed only on the top of the product in the center of each part of the sash. They move along the upper guide, the lower one is missing. Folding of a cloth is provided by usual door loops.
