Full Extension vs Partial Extension: Definition & Difference in Cabinet Making

June 28, 2026

A full extension allows a drawer to be pulled out of the cabinet carcass by 100%, making the entire interior accessible right up to the back panel. A partial extension, on the other hand, can only open to roughly 75% to 80% due to its design. The rear section of the drawer remains inside the cabinet, which restricts access to the back area.

What is the precise difference?

The mechanical difference between both runner types lies in the construction of the profiles. A partial extension generally consists of two track profiles (the carcass profile and the drawer profile). When the runner reaches its maximum stop, a portion of the drawer remains anchored inside the carcass to absorb the leverage effect and prevent tilting.

A full extension, by contrast, utilises a three-part telescopic principle. An intermediate profile bridges the distance, allowing the drawer runner to travel fully clear of the carcass front edge. You notice the difference in everyday use, much like reaching into a deep storage box: with full extension, the entire contents are clearly laid out before you, whereas with partial extension, you have to fumble blindly in the rear third.

Runner types and mechanisms

Both full and partial extension runners come in various technical designs, selected according to the furniture piece and application requirements:

Roller runners: The simplest design, where nylon rollers run inside an epoxy-coated steel profile. They are frequently designed as partial extensions. Suitable roller runner drawer runners are usually bottom-mounted.
Ball bearing runners: Here, small steel balls inside a ball cage ensure smooth running. This design is the standard for full extension drawer runners and is screwed to the side of the drawer box.
Undermount runners: The runner mechanism is mounted completely concealed beneath the drawer base. Undermount drawer runners provide a clean appearance and high lateral stability.

Regarding convenience features, a distinction must be made between two contrasting mechanisms: Soft-close damping slows the drawer down upon closing and pulls it shut gently (soft-close drawer runners). Push-to-open (tip-on) is the exact opposite: pressing the handleless front triggers a spring mechanism that pushes the drawer open slightly (push-to-open drawer runners). Both systems require precise gap dimensions during installation.

Dimensions, standards, and typical values

When planning drawer systems, nominal length and installation clearance are vital.

Lengths: Runner lengths correspond to the depth of the cabinet carcass and are usually stepped in increments of 50 mm (from 250 mm - 800 mm). For standard kitchen base units, 500 mm drawer runners are frequently used. For narrow bathroom units or chests of drawers, one is more likely to choose 350 mm drawer runners.
Installation clearance: For side-mounted ball bearing runners, a defined space must be left between the drawer side and the carcass inner wall. The industry standard dimension here is precisely 12.7 mm (equivalent to half an inch) per side.
Load capacity: A standard runner typically carries between 25 kg and 35 kg. For workshop trolleys or deep pan drawers, heavy-duty drawer runners are required; using thicker steel and larger ball cages, these withstand loads from 45 kg to over 100 kg.

Usage & Selection

The choice between full and partial extension depends on the intended purpose. Full extension is technically more complex, but offers maximum convenience. It is the standard choice for kitchen drawers, filing cabinets, and deep pull-outs where an overview of the entire contents is strictly necessary.

Partial extension is an economical solution for furniture where complete access is not critical. Typical areas of application include shallow desk drawers for stationery, small bedside tables, or simple chests of drawers for clothing.