Installing Concealed Undermount Drawer Runners: Step-by-Step Guide for Invisible Fittings

January 13, 2026

An undermount runner is fitted completely concealed beneath the drawer base, providing an immaculate aesthetic for furniture through hidden hardware.

Installing concealed runner systems requires precision during the planning and manufacturing of the drawer box. Unlike side-mounted runners, undermount installation tolerates far fewer dimensional discrepancies during timber cutting. This guide is aimed at joiners, fitters, and experienced DIYers wishing to integrate a drawer box with a concealed runner level into a cabinet carcass. Fitting time takes approximately 15 to 25 minutes per drawer with prepared components.

Planning and Construction of the Drawer Box

Before the runners are fastened inside the cabinet, the drawer box must feature the exact routings and dimensions required for the chosen system. The runner mechanism sits beneath the drawer base, which requires a specific construction.

Base Recess: The drawer base must not sit flush with the bottom edge of the side panels. It must be grooved in with a 12 mm to 15 mm upward offset to create room for the runner mechanism.
Back Panel Cut-out: The rear panel of the drawer must be narrower at the bottom edge than the side panels or feature corresponding cut-outs. This is where the rear locking hooks of the runner engage.
Drill Holes in the Back Panel: Precisely positioned holes (usually 6 mm in diameter) must be drilled into the rear panel to accommodate the runner's rear locating pins.
Internal Carcass Width: The external width of the drawer is determined by the internal cabinet width minus a fixed system dimension. For a drawer side panel thickness of 16 mm, this deduction is often exactly 42 mm.

Required Tools and Materials

To ensure precise installation within the cabinet carcass and onto the drawer, prepare the following tools and components:

Undermount runner (as a full extension or single extension) in the appropriate nominal length (e.g. 400 mm, 500 mm, or 600 mm)
One pair of front locking clips (catch couplings)
Chipboard screws (countersunk, 3.5 x 15 mm or 4 x 15 mm) or Euro screws (6 x 13 mm)
Cordless screwdriver with matching PZ or TX bit
Folding rule or tape measure
Joiner's try square
Pencil and bradawl
Wood drill bits (3 mm for pilot holes, 5 mm for the System 32)

Anyone wishing to gain an overview of different runner systems will find the right technical specifications for their project under undermount drawer runners.

Step-by-Step: Fitting Undermount Runners

The following guide describes the standard procedure for common systems equipped with a front locking clip and a rear locating pin.

1. Marking the Runner Position in the Carcass

Installation inside the cabinet starts with positioning height and depth. The frontmost fixing screw of the runner usually sits 37 mm from the front carcass edge. This corresponds to the standard dimension in System 32. The height of the first runner depends on the desired position of the drawer. Ensure you factor in the required bottom clearance (usually 2 mm to 5 mm) so that the drawer front does not rub against the cabinet base when opening. Mark the drilling points on both carcass sides completely parallel using a square.

2. Screwing the Runner Profiles into the Cabinet

Position the carcass runner along the marked line. Screw the profile securely to the side panel. If a pre-drilled line of holes is available, use Euro screws in the 5 mm drillings. On plain side panels, use chipboard screws (3.5 x 15 mm) and drive them through the small round holes of the runner. Insert at least three screws per runner (front, centre, rear); for heavier versions from the heavy-duty drawer runners range, insert more accordingly to transfer the load capacity of 40 kg or more safely into the carcass panel.

3. Fitting the Locking Clips to the Drawer

Turn the prepared drawer box over so that the underside faces upwards. The locking clips are placed flush into the front left and right inner corners between the side panel and front piece. Fasten each locking clip using two to three small screws driven diagonally into the front and straight into the side panel. These components subsequently connect the drawer securely to the runner and enable height adjustment.

4. Inserting the Drawer (Marriage)

Pull both installed runners in the cabinet fully forward. Place the drawer box horizontally onto the runners. Now slide the drawer backwards into the cabinet with even pressure. The drawer glides along the runners into the carcass like a carriage on accurately levelled rails. At the end of the insertion travel, you will hear a distinct click. This indicates that the front clips have locked into the runner and the rear pin has engaged with the back panel hole.

5. Adjusting the Gap Alignment

Modern undermount systems offer tool-free 3D adjustment directly on the locking clip or runner.

Height adjustment: A small lever on the clip usually allows the front to be lifted by up to +3 mm.
Side adjustment: A small thumbwheel on the underside shifts the drawer by ±1.5 mm to the left or right.
Tilt adjustment: On deep drawers, a lever is often located at the rear of the runner to adjust the tilt of the front gaps.

Avoiding Common Installation Mistakes

Even experienced fitters occasionally make mistakes during the construction and assembly of concealed drawer systems, affecting the drawer's running performance.

Incorrect Internal Drawer Clearance If the drawer jams when pulled out or cannot be inserted at all, the external drawer width has often been calculated incorrectly. If the drawer is just 1 mm to 2 mm too wide, the roller carriages rub against the profiles. Scrupulously check the manufacturer's deduction dimensions before cutting the base panel.

Confusing Dampers and Automatic Opening Mechanisms A critical planning error is conflating different closing mechanisms. Soft-close (damping) draws the drawer closed softly and with braking action over the final centimetres. Such systems can be found under soft-close drawer runners. In total contrast is the tip-on or push-to-open function. Here, the drawer opens handle-free via spring force when pressure is applied to the front. Both systems require entirely different installation gaps for the front. A sprung solution strictly requires a trigger gap of 2.5 mm to 3 mm between front and carcass. Corresponding fittings are listed in the category for push-to-open drawer runners.

Missing Back Panel Hole If the 6 mm hole in the drawer back panel is missing, the runner's rear locating pin cannot engage. The drawer tilts downwards when fully extended, which, under heavy loads, leads to the front locking clips tearing out.

Extended Features: Full Extension vs Single Extension

When selecting drawer runners, two basic extension types are available, differing in construction and utility.

A full extension runner can be pulled 100% out of the carcass. If the runner has a nominal length of 500 mm, the extension travel is likewise 500 mm. The entire interior of the drawer is unobstructed and accessible from above. This is achieved via a three-part telescopic profile inside the runner. For kitchen units or deep office furniture, this version is strongly recommended for ergonomic reasons. Matching models can be found under full extension drawer runners.

A single extension (part extension) runner can only be opened to about 75% to 80%. With a nominal length of 500 mm, roughly 100 mm of the drawer remains inside the cabinet. The rear area remains concealed. Single extensions consist of only two nested profiles, making them mechanically simpler and less susceptible to faults under extreme loads, though user convenience is reduced.

FAQ – Frequently Asked Questions about Undermount Installation

Can I replace an old roller runner with an undermount runner? A direct like-for-like swap is not possible without altering the drawer box. A classic side-mounted roller runner typically requires 12.5 mm of clearance per side and a flush drawer bottom. An undermount runner strictly demands the specified base recess of 12 mm to 15 mm as well as specific cut-outs on the rear panel. The drawer box must be built entirely anew or extensively re-routed for the conversion.

What does nominal length mean for drawer runners? The nominal length (NL) indicates the installation depth of the runner in the carcass and generally corresponds to the external length of the drawer box (excluding the front). A runner with an NL of 500 mm requires an internal carcass depth of at least 503 mm.

What is the load capacity of a standard undermount runner? Common systems for residential use are designed for dynamic loads of 30 kg. For wide kitchen pan drawers or workshop units, reinforced profiles exist that can support 40 kg to 65 kg. The weight of the drawer itself must always be included in the load calculation.

Are there undermount runners with self-closing action without damping? Yes, this mechanism is referred to as a self-closing runner. The drawer is drawn closed over the final centimetres mechanically via a spring, but without hydraulic braking. Such variants are found under self-closing drawer runners. They close audibly, but ensure the drawer does not accidentally remain ajar.