A corredor del cajón (drawer slide) is the mechanism that carries a drawer in and out of the carcass. Two families dominate: side-mounted ball-bearing runners, which fix to the outside of the drawer box, and undermount runners, which fix beneath it.
Two families, two costs
A side-mounted runner fixes to the side of the drawer box and to the inside face of the carcass. It is visible when the drawer is open and it takes about 12.5 mm off each side of the drawer — roughly 25 mm of usable width. It is cheap, strong and easy to fit.
An undermount runner fixes beneath the box. Nothing is visible, the full internal width is available, and the drawer closes with a soft-close action as standard. The cost is height: the mechanism needs clearance under the drawer, and a deeper drawer box to carry the fixing.
| Propiedad | Montaje lateral | debajo del montaje |
|---|---|---|
| Visibilidad | Visible when open | Oculto |
| Width lost | About 25 mm total | Ninguna |
| Height lost | Ninguna | 20–30 mm under the box |
| Capacidad de carga | 25-35 kg | 30-45 kg |
| Cierre suave | Opcional | Generalmente estándar |
| Coste relativo | Bajo | Medio alto |
Extension and load
Extension is how far the drawer comes out: three-quarter, full, and over-travel. Full extension is the practical minimum for a kitchen, because a three-quarter drawer leaves the back 25% of the box inaccessible under a benchtop.
Load ratings fall as length rises. A 45 kg runner at 450 mm may be rated 35 kg at 600 mm — the rating is for a specific length, and quoting the headline figure without the length is how drawers end up overloaded. Check the rating at the length you are actually using.
What actually fails
The clip that holds the drawer to the runner, not the runner itself. A drawer that is lifted out repeatedly — by a cleaner, by a tenant — spreads the clip and starts to click. Buy runners with a metal clip rather than a plastic one on anything that will be removed often.
The second failure is alignment. A carcass that is 2 mm out of square makes one runner bind at the front and another at the back, and no adjustment at the drawer fixes a twisted box.
Preguntas frecuentes
Side-mount or undermount?
Undermount for anything specified to feel solid and to use the full drawer width. Side-mount where cost is the constraint and the sides of the drawer are not seen.
How much width do side-mounted runners take?
About 12.5 mm per side, 25 mm in total. A 500 mm cabinet opening gives roughly 475 mm of drawer width.
What does load rating mean?
The weight the runner carries at a specific length, tested over a stated number of cycles. A 45 kg rating at 450 mm may drop to 35 kg at 600 mm.
Can I convert side-mount to undermount?
Not on the same drawer box. The box has to be rebuilt — narrower, with a base that takes the fixing — and the carcass may need new holes.
