Shelf Supports for Cabinets: Pin Size (3mm vs. 5mm) and Load Capacity

May 13, 2026

A shelf support is a connecting fitting inserted into the pre-drilled row of holes in a cabinet side panel to support shelves. The standardised pin size in furniture construction is usually 3 mm or 5 mm, while the load capacity depends on the material properties of the support, the depth of the shelf, and the number of support points.

What exactly is a shelf support?

In furniture construction, the shelf support serves to transfer vertical loads. It directs the weight of the shelf and the items placed on it into the carcase of the furniture piece. The operating principle is simple yet requires mechanical precision: the support consists of a pin that engages positively into the carcase wall, and a bearing surface on which the shelf rests. Much like a load-bearing anchor point on a climbing wall, the pin must sit precisely within the drilled hole to prevent tear-out under load.

Depending on the furniture design, these fittings can be found in virtually every type of cabinet, from overhead kitchen units to large wardrobes for 2 people.

The pin size: 3 mm or 5 mm?

The hole in the cabinet side defines the required pin size. In industrial furniture manufacturing and joinery, two standards have become established:

5 mm pin size: This is the absolute industry standard, based on the standardised System 32. In this system, the drilled holes in the row have a spacing of exactly 32 mm from each other and a diameter of 5 mm. A 5 mm thick steel pin provides high shear strength.
3 mm pin size: This more delicate option is used in furniture where unused holes in the row should be less visually noticeable. However, the thinner material thickness of the pin results in reduced shear resistance.

Types and variants of shelf supports

Choosing the right support depends on the material of the shelf and the required fixing method. Within the category of shelf supports, the following basic types are distinguished:

L-shaped shelf supports (angled shelf brackets): The shelf rests on a flat bracket. Often, this shelf support features an additional hole to secure the wooden shelf from below using a chipboard screw (usually 3 mm diameter). This prevents the shelf from slipping.
Cylindrical shelf supports (plug-in pins): A simple, continuous cylinder made of metal or plastic. The shelf rests directly on the rounded surface. A variant is the spoon shelf support with a flattened bearing area.
Glass shelf supports: Because glass shelves can scratch or splinter on direct contact with metal, glass shelf supports feature a soft pad made of plastic or rubber. Some models also clamp the glass pane to prevent tipping.

Load capacity and material choice

The permissible load capacity is generally specified per shelf (when using four supports). Typical ratings for standard cabinet shelves range between 15 kg and 50 kg.

The actual load-bearing capacity depends on three factors:

Material of the support: Models made of steel or solid die-cast zinc carry significantly more weight than pure plastic designs.
Condition of the carcase wall: With soft chipboard, it is often not the steel pin that gives way under extreme stress, but the drilled hole that tears out.
Leverage effect: The deeper the cabinet, the greater the leverage acting on the front supports.

For installations that must hold extremely high loads, simple plug-in pins are often insufficient. In these cases, screw-mounted shelf brackets on the wall or complete wall shelving units with heavy-duty brackets are used instead.

Installation and drill hole depth

For a secure installation, the drilling depth of the hole row must match the length of the pin. A standard pin usually has a length of 7 mm - 9 mm. The hole should therefore be at least 8 mm - 10 mm deep to ensure the fitting sits flush against the cabinet wall. If the support is not fully inserted into the hole, leverage is created that widens the drill hole.

Even with low furniture, such as a TV sideboard, a secure fit for shelves must be ensured, particularly when heavy electronic equipment is placed on them.