Undermount slides hide below the box and pull it shut with a soft close motion, which is why they feel like the good drawers in a showroom kitchen. They are fussier to install than side mount slides because the box has to be built for them. Here is how the system goes together with a Blum undermount set.
Quick answer. Undermount slides need a drawer box built for them: notched and drilled at the back so the runner’s hook seats, with locking devices clipped to the front and the width sized to the slide, not the opening. Mount the runners in the cabinet, drop the box onto them, then let the locking devices click the front home. Gritly preps every custom box for the exact runner you name, so the notch, hook hole and width already match before it ships.
What undermount slides need from the box
An undermount slide carries the drawer from underneath, so the box bottom and back do the work. Two things have to be right or the box will not sit on the runners:
- The box back is notched and drilled so the runner’s own rear hook can seat in it. The locking devices are a separate part that clips in at the front.
- The bottom is set into a groove at the correct height, and the box width is sized to the slide, not to the opening.
We cut every undermount box to the exact slide you choose, so the notches and width are already correct when it arrives. Tell the configurator your slide model and the box comes ready to drop on.
Step 1: mount the runners in the cabinet
The runners screw to the cabinet floor or to the side, tight to the front edge and level front to back. In a frameless cabinet they sit flush to the front. In a face frame cabinet you usually need a rear socket or a front bracket so the runner starts at the frame. Set both runners at the same depth so the box sits square.
Step 2: set the locking devices on the box front
The locking devices are the small clips that press into the front bottom corners of the box. On most Blum sets they press into place by hand. These are the parts that latch onto the front of the runner when you lower the box, so seat them fully.
Step 3: hang the box and engage
Extend both runners toward you. Tip the box back down first and engage the rear hooks into the rear notch and hook holes, then lower the front until the locking devices click onto the runners. Push the box in and it should latch and soft close the last stretch on its own.
Step 4: dial in the fit
Blum undermount slides adjust three ways from the locking devices: height, side to side, and depth for the front reveal. Set the front flush and even with its neighbors. The full walkthrough is in how to adjust undermount slides.
Order a box built for your slide
The single thing that makes undermount installs go wrong is a box that was not built for the slide. See the slide models and depths we notch for on our drawer boxes for Blum undermount slides page, then configure a box to the 1/32 inch and pick your slide. It arrives notched, sized and ready.
Shop undermount slides, clips and install parts
Everything this install needs is in our shop: the runners, the locking clips, the rear sockets for face frame cabinets, and the screws.
- Würth PRO600 and PRO634 undermount slides
- Blum Movento 763, 769 and Tandem 563F slides
- Würth FCLIP3D, Blum Movento and Blum Tandem locking clips
- Rear mounting sockets for step 1 in face frame cabinets, and euro and slide screws
Undermount install questions
What does a drawer box need for undermount slides?
A notched and drilled back so the runner’s own rear hook can seat, locking devices at the front that clip onto the runner, a bottom set into a groove at the right height, and a width sized to the runner and the opening. Order the box for the exact slide model and all of it is done before it ships.
Where do the locking devices go?
Into the front bottom corners of the box, one left and one right. On most Blum sets they press in by hand and click onto the front of the runner when you lower the box.
How do I adjust the front after the install?
From the locking devices: height, side to side and depth, a few millimeters each. The adjustment guide shows where each adjuster sits.
How to install undermount drawer slides?
Undermount installation has three parts: screw the runners into the cabinet level and at the setback the maker’s sheet gives, lower the box so its notched back engages the runner’s rear hook, then let the front locking clips click onto the runners. The steps are the same for Blum and the other undermount brands Gritly notches for. Order the box already cut to your exact runner and it fits on the first try.
Will any drawer box work with undermount slides?
No. Undermount runners carry the box from underneath, so the back has to be notched and drilled for the runner’s rear hook and the width has to match the slide, not just the opening. A box built for side mount or bottom mount will not sit on undermount runners without that prep. Gritly cuts every custom box with the exact notch and width your chosen runner needs, so ordering it for undermount slides is a dropdown pick, not an extra step.