DUO-System – Frame Connectors

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The DUO-System is strategically engineered for fast processing while maintaining a design of traditional frame joints in furniture making. The DUO-System is simple and easy-to-use, even for the end user.

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Furniture and interior design, beds, stairs, booths, and any other smaller timber constructions.

The DUO SYSTEM provides the optical qualities of traditional frame joints while being engineered in an innovative manner for fast processing and application. For example, the DUO 100/15 is an ideal frame connector for beds, and, like all KNAPP connectors, is non-visible, can be disassembled, self-tightening. It is so quick and easy to assemble that even the end user can do it. Beds made with the DUO 100/15 provide the perfect finished look with no visible fastener parts.
The wood component can shrink and swell, while the joint can be adjusted and re-tightened via the screws of the fastener.

  • Non-visible – concealed, self-tightening column and beam connectors.
  • User-friendly – disassembly possible if needed.
  • Self-tightening – through adjusting of the screws.
  • Efficient – high degree of pre-manufacturing.
  • Simple transport – components can be transported and simply assembled on site.
  • Fast – efficient and very good to use in production line manufacturing.
  • Safe – tested by HFA (Holzforschung Austria).
  • Adjustable – the connector can be adjusted as needed.

DUO 26/26

DUO 46/15

DUO 62/15

DUO 100/15

DUO 46/30

DUO 62/30

DUO 90/20

DUO 90/46

By screwing with CS-screws Ø 5 mm or Ø 6 mm (Length as required) and PH-screws Ø 5 mm or Ø 6 mm
Concealed, self locking, by adjustable screw connector, for frame connections
With CNC-Machine, Long hole drilling machine, Hand router
Suitable materials
All solid and plywood materials from 21 mm
Frame connections for furniture, stairs and Stand construction to Interior design


Furniture and Interior Design





Click the link to view and download our Instruction Manual for the DUO System: 26/26, 46/15, 62/15, 100/15, 46/30, 62/30, 90/20, 90/46

The Duo system is non-visible as it is installed in a groove with a depth of 13 mm and milled either into the end-grain or face-grain of the wood component. You can use a hand router and/or a CNC machining center with a Ø 15 mm cutter to do the groove. The joint is always tight, as the connector snaps together in a dovetail-like manner. Still, the fasteners allow the natural shrinking and swelling of the joints and are adjustable if needed. The DUO System connector consists of two identical connector parts, made of high strength blue-galvanized weather-resistant steel, and is manufactured in Austria.
The choice of the correct DUO connector size depends on the used timber dimension. The milling operations can be made optionally with a hand router or a CNC machining center. Drilling and millings jigs are available if needed. The system is tested and available in eight different sizes.

Load values

The load value refers to the transverse force in the insertion direction.
Details of the stress values are of the certificate of Holzforschung Austria from 02.11.2000 and the current KNAPP catalogs.
In DUO systems are commercially CS-screws (5×40, 5×60, 6×40, 6×60 mm) according to Ö-Norm M5027 should be used.

F0 0,86 kN*
DUO 46/15
F0 0,97 kN*
DUO 26/26
F0 1,29 kN*
DUO 62/15
F0 1,30 kN*
DUO 46/30
F0 2,00 kN*
DUO 100/15
F0 2,15 kN*
DUO 62/30
F0 2,37 kN*
DUO 90/20
F0 4,35 kN*
DUO 90/46