Adjusting Mechanical Flap Stays Correctly: Opening Angle and Braking Effect

November 20, 2025

Mechanical flap stays support upward-opening furniture fronts through adjustable friction, whilst gas struts push the flap open using compressed gas in cylinders with a defined force in Newtons.

The design and adjustment of flap mechanisms require precision. A furniture front opening upwards is subject to gravity and leverage. If the front drops shut again after opening or slams loudly against the cabinet carcass during closing, the mechanism is incorrectly dimensioned or poorly adjusted. This guide explains the technical differences between mechanical stays and gas struts, shows how to calculate the required holding force, and guides you through proper installation and adjustment.

Key Buying Criteria for Flap Mechanisms

When selecting the appropriate flap fittings, the front weight, carcass height, and desired opening angle determine the hardware specifications.

Load capacity and holding force: Mechanical stays work via frictional resistance that holds the weight of the front. Gas struts utilise compressed nitrogen. Here, the force is specified in Newtons (N). As a rule of thumb, 10 N corresponds to a lifting capacity of roughly 1 kg.
Flap weight: The weight is calculated from the volume of the front panel and the material density (e.g. MDF or chipboard at approx. 700 kg/m³). The handle weight must also be added, as it sits at the outermost leverage point.
Carcass height: The height of the cabinet determines the maximum stroke length (stroke) of the strut. Common lengths for standard wall units range between 250 mm and 270 mm in the extended state.
Opening angle: Standard flaps are typically adjusted to 75°, 90°, or 110°. An angle of 110° provides complete access to the interior, but requires that the user can still comfortably reach the raised handle edge.

Overview of Types and Options

Different systems are used depending on the application and the weight of the front.

Mechanical Flap Stays (Friction Stays)

Classic mechanical flap stays consist of two metal arms connected by a pivot joint. The holding force is generated via a central adjustment screw at the joint. Similar to a disc brake, friction discs are pressed together here. The tighter the screw is turned, the higher the resistance. These systems allow the flap to remain stationary at any position (multi-position stop).

Gas Struts

A gas strut pushes the flap open automatically to its end point after being lifted slightly by hand. The force is factory-set (typically 50 N, 60 N, 80 N, 100 N, 120 N, or 150 N) and cannot be altered using a screw. They do not stop at intermediate positions, but always extend to their maximum stroke. For aesthetic integration into the carcass, they are available in various finishes, such as gas struts silver, gas struts white, or gas struts black.

Heavy-Duty Systems

For large fronts made of solid wood or thick MDF panels, standard models are often insufficient. In these cases, dedicated gas struts for heavy flaps must be installed. These feature thicker cylinders and provide forces ranging from 150 N to over 200 N each.

Which System for Which Application?

Choosing between mechanical stays and gas struts depends on the desired user convenience and the cabinet geometry.

If the flap needs to stay open at various angles (e.g. on very high wall units where an 110° opening puts the front out of reach), then choose a mechanical friction flap stay.
If the front should lift open automatically and effortlessly to its limit stop, then a gas strut is the ideal choice.
If the front is wider than 600 mm or heavier than 4 kg, then you must fit two fittings (one on the left, one on the right) to prevent hinge misalignment (twisting).
If you have a very lightweight front (e.g. aluminium frame with acrylic glass), then select the lowest force gas strut (50 N or 60 N) or a light mechanical stay. A strut that is too strong could tear the front from its hinges during opening or make closing extremely difficult.

Installation and Adjustment: Setting Opening Angle and Braking Effect

Proper function of the flap depends largely on the accurate positioning of the fixing points on the carcass and front panel.

Required Tools

Tape measure and pencil
Bradawl or 2 mm wood drill bit
Cordless screwdriver with a PZ2 (Pozidriv) bit
Matching Allen key (usually 4 mm) for mechanical stays

Step 1: Determine Mounting Points

With gas struts, the opening angle (75°, 90°, or 110°) is determined solely by the position of the fixing points. A dimension sheet is supplied with the fittings. For a 90° angle, the carcass mounting bracket is usually fitted approx. 250 mm below the top panel and set back 25 mm from the front edge. The bracket on the front sits approximately 90 mm from the hinge pivot point. These dimensions vary depending on the manufacturer and stroke length.

Step 2: Check the Hinges

Flap stays support the front panel; they do not replace the hinges on the top panel. Use standard concealed cup hinges with a full overlay. The hinges should ideally have no self-closing spring mechanism when combined with gas struts, as opposing forces can disrupt smooth movement.

Step 3: Adjusting Braking Effect on Mechanical Stays

Fit the stay according to the specified dimensions.
Open the flap to the desired position (e.g. 90°).
Insert the Allen key into the central joint screw.
Turn the screw clockwise to increase friction.
Release the front. If it drops, increase the tension further. If it stays in place but is very difficult to close, loosen the screw slightly anti-clockwise.

Step 4: Adjustments for Gas Struts

Since gas struts cannot have their force adjusted, the installation geometry must be precise. If the flap snaps open too forcefully, the front mounting plate can be shifted a few millimetres towards the hinge. This alters the leverage ratio and reduces the opening force at the stop.

FAQ – Frequently Asked Questions About Flap Installation

How do I calculate the required force in Newtons for my gas strut? Weigh the door including the handle. Multiply the weight in kilograms by 10. Example: A 3.5 kg front theoretically requires 35 N. Since gas struts can lose a small amount of pressure over the years, add a 10 to 20 % safety margin. In this case, choose a 50 N strut.

Why is the flap dropping on its own? With mechanical stays, the adjustment screw at the pivot joint is too loose; the frictional resistance is insufficient to support the weight. Tighten the screw. With gas struts, either the fitting is undersized for the front weight (too few Newtons), or the cylinder has lost its gas due to wear. In this case, the strut must be replaced.

Can the opening angle of gas struts be changed via an adjustment screw later? No. The extended position of the cylinder is fixed. The angle can only be modified by repositioning the screw mounting points on the carcass and front according to the manufacturer dimension tables.

How many flap stays do I need per front? For front widths up to 400 mm and low weight, a single stay on one side is often sufficient. From 400 mm in width or a weight over 3 kg, two fittings (left and right) must be fitted. A one-sided load will eventually cause the front to twist and damage the concealed hinges.

What is the difference between a flap stay and a flap damper? A flap stay (mechanical or gas-assisted) holds the front up when open. A furniture damper (soft-close buffer), on the other hand, cushions the front over the final few millimetres of closing so it does not slam loudly against the carcass.