H27 and H35 Drawer Runner Heights: Precise Matching and Replacement of Ball Bearing Slides

The profile heights H27 and H35 for telescopic runners define the exact overall height of the guide rail in millimetres and are crucial for precision fitting during side mounting or when replacing runners within a routed groove.

H27 and H35 Runner Heights: Fundamentals and Classification

When repairing or building cabinetry, choosing the exact runner height is vital for the proper operation of the drawer. The designations H27 and H35 refer to the vertical height of the metal profile of a ball bearing runner. While H27 (27 mm height) is frequently used for shallow drawers, keyboard trays, or lightweight office furniture, H35 (35 mm height) is the standard dimension for medium loads in living room and bedroom furniture.

Swapping between these two heights is generally not possible without modifying the furniture. If the runner height does not match the existing hole pattern or side groove, the drawer front will collide with the carcass or the runner will jam completely.

Key Technical Criteria for Replacement

Before replacing a defective slide, the geometric and mechanical parameters must be precisely determined.

Installation Width (Side Clearance)

Regardless of the H27 or H35 profile height, ball bearing telescopic runners require a defined side clearance between the drawer box side and the interior carcass wall. For most models, this measurement is exactly 12,7 mm (half an inch) per side. A deviation of more than 0,5 mm leads to rough running or premature wear of the ball bearings.

Extension Length and Nominal Length

The nominal length of the runner must correspond to the depth of the drawer box, but must not exceed the internal depth of the carcass. In furniture construction, lengths are typically graded in 50 mm increments. For standard chests of drawers, drawer runners 300 mm or drawer runners 450 mm are commonly fitted.

Extension Type: Full Extension vs Partial Extension

This feature defines access to the stored items.

• A full extension runner extends to 100%. The drawer pulls out completely from the carcass. This is achieved via a three-part runner profile.
• A partial extension runner reveals only about 75% of the drawer depth. The rear quarter remains inside the carcass. This mechanism is usually based on a two-part profile.

If you require maximum access, you should consistently opt for full extension drawer runners when replacing fittings, provided the profile height and side clearance match.

Load Capacity

The load capacity is stated in kilograms per pair. H27 runners are typically designed for loads up to 15 kg. H35 runners can carry 20 kg - 30 kg depending on the material thickness. If tool cabinets or heavy larder drawers are planned, these profile heights are often insufficient. In such cases, wider profiles such as heavy duty drawer runners with load capacities from 45 kg must be used.

H27 vs H35 – Types and Mechanisms Overview

The profile height often dictates the available comfort features. Fitting a runner into an existing routed groove is like fitting a piston in a cylinder – the clearance must be accurate to the millimetre, otherwise the mechanism will bind.

H27 Telescopic Runners

• Profile: Usually two-part (partial extension) or very compact three-part design.
• Area of application: Shallow drawers where an H35 runner physically cannot fit (e.g. beneath a desk top).
• Fitting: Often surface-mounted to the drawer side or set into a shallow side groove.

H35 Telescopic Runners

• Profile: Almost exclusively three-part (full extension).
• Area of application: Standard drawers in chests of drawers, bathroom furniture, and wardrobes.
• Comfort options: Additional mechanisms are widespread in the H35 category.
• Soft-Close: An integrated damper catches the drawer over the final centimetres and pulls it shut smoothly and quietly. (See: soft close drawer runners).
• Push-to-Open: A spring mechanism pushes the handleless drawer open following light pressure on the front panel. (See: push to open drawer runners).
• Note: Soft-close and push-to-open are opposing mechanisms and are physically mutually exclusive within a single runner.

Decision Guide: Which Runner for Which Scenario?

The choice of the correct runner is usually predetermined by the furniture piece during a replacement, but can be freely chosen for a new build.

• When replacing an old grooved slide: Measure the height of the groove. If it measures exactly 17 mm, you require a dedicated 17 mm groove runner, not a standard H27 runner. If the groove is wider (e.g. 27 mm or 35 mm), select the exact profile height that was previously fitted in order to reuse the System 32 drill holes.
• When converting from roller runners to ball bearing runners: Traditional roller drawer runners are mounted beneath the drawer base and often require only 1,5 mm to 2 mm of side clearance. A ball bearing runner (H27 or H35) is side-mounted and strictly requires 12,7 mm of space per side. A direct replacement is not possible without narrowing the width of the drawer box.
• When outfitting deep furniture carcasses: Utilise the full available depth. For deep cupboards, drawer runners 500 mm or drawer runners 600 mm are ideal. For these lengths, ensure you select a full extension model, as partial extension runners leave over 150 mm concealed inside the cabinet.

Installation Advice for Telescopic Runners

Fitting ball bearing drawer slides requires precision.

Required Tools

• Cordless screwdriver
• Cross-head screwdriver bit (PZ or PH, depending on the screw)
• Tape measure / folding rule
• Spirit level or try square
• Bradawl or centring drill bit (3 mm)

Installation Steps

1. Separate the runner: Pull the runner out completely. Operate the small plastic release lever inside the profile. The narrow inner profile (carcass member) can now be fully detached from the outer profile (drawer member).
2. Fit the inner profile to the drawer: Screw the narrow profile centrally onto the drawer side. Use flat-headed wood screws (e.g. pan head, 3,5 x 16 mm). Countersunk screws can obstruct the ball bearing cages if they do not sit perfectly flush.
3. Fit the outer profile to the carcass: Align the wide profile horizontally on the inside wall of the carcass. Use the slotted holes for vertical and horizontal fine adjustments.
4. Reassembly: Guide the drawer with the attached inner profiles horizontally into the ball cages of the outer profiles. Push the drawer in with gentle pressure until it reaches the stop and the release lever clicks audibly into place.

Frequently Asked Questions (FAQ) About Runner Heights

Can I replace an H27 runner with an H35 runner?

No, typically not without alterations. An H35 runner is 8 mm taller. If the runner sits in a precisely routed groove, the taller profile will not fit. Furthermore, the horizontal drilling patterns will shift, resulting in misaligned drawer fronts.

What does full extension mean on a 35 mm runner?

The drawer can be pulled out to 100% of the runner length from the carcass. On a 400 mm runner, the drawer extends exactly 400 mm out of the unit, allowing full access to the back of the drawer.

What side clearance is required for H27 and H35 runners?

Both profile heights require an exact installation gap of 12,7 mm (tolerance + 0,2 mm / - 0 mm) between the outer side of the drawer and the inner wall of the carcass for ball bearing telescopic runners.

Can H35 runners feature both soft-close and push-to-open simultaneously?

No, these mechanisms are physically incompatible. A damper (soft-close) actively pulls the drawer shut over the last few centimetres and holds it closed. A push-to-open mechanism requires pre-tension to push the drawer open when pressed. Both functions cannot be combined within a single runner.

Which screws should I use for installation?

Use chipboard screws with a pan head in 3,5 mm or 4 mm diameter. The drive type is typically PZ (Pozidriv). The flat head ensures that the screw does not protrude past the metal profile and damage the ball bearings as they slide past.

Matching Lengths for Your Project

Selecting the correct nominal length is just as important as the profile height. Always match the length to the available internal carcass depth. For very shallow units, such as key cabinets or wall-hung bathroom cupboards, drawer runners 250 mm are suitable.

For standard residential furniture, lengths between 350 mm and 500 mm are ideal. If you are looking for a solution that keeps the drawer reliably closed without complex damping systems, a variant with a simple retention mechanism is recommended (see: self closing drawer runners). Always verify the exact measurement of the profile height when placing your final order to ensure an effortless installation.