Undermount vs Side-Mount Drawer Slides?
By Nate Sawyer, Editor · Updated July 2026
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Blum TANDEM plus BLUMOTION 563H Undermount Drawer Slide (21 in)
Blum's TANDEM plus BLUMOTION 563H is the gold-standard 21 in undermount slide: it hides fully under the drawer for a clean furniture look, carries 100 lb with buttery soft-close, and offers 4-way adjustment. But the required front locking devices aren't included, it demands a precisely built drawer box, and it costs far more than side-mounts.
| Type | Undermount, concealed, full extension |
|---|---|
| Length | 21 in (9–21 in available) |
| Load rating | 100 lb |
| Soft-close | Yes (integrated BLUMOTION) |
| Extension | Full extension |
| Drawer material | 1/2 in–5/8 in sides |
| Adjustment | 4-dimensional (height, tilt, side, depth) |
Liberty D80622C 22 in Side-Mount Ball-Bearing Full-Extension Slide
Liberty's D80622C is a 22 in side-mount, ball-bearing full-extension slide, the cheap, forgiving workhorse for shops, closets and budget kitchens. It glides smoothly and carries 100 lb. But the 1/2 in slide shows on each side, this base model has no soft-close (a pricier version adds it), and it needs exactly 1/2 in clearance per side.
| Type | Side-mount, ball-bearing, full extension |
|---|---|
| Length | 22 in (16–24 in available) |
| Load rating | 100 lb |
| Soft-close | No (soft-close model 942205 available separately) |
| Extension | Full extension |
| Clearance | 1/2 in per side required |
| Finish | Zinc plated steel |
Our verdict
Undermount slides (Blum Tandem) hide completely under the drawer, add integrated soft-close, and give a premium look — but they cost more, need locking devices, and demand a precisely built drawer box. Side-mount ball-bearing slides (Liberty) are cheaper, stocked everywhere, and far more forgiving to install, at the cost of a visible slide on each side and no soft-close on the base model. For a kitchen reno where drawers carry weight and you want them invisible, choose undermount. For a workshop, closet, garage, or budget build — or any drawer box that isn't perfectly square — side-mount is the smarter, easier pick.
Frequently Asked Questions
- Can you use side-mount drawer slides as undermount slides?
- No - they are built for different mounting geometry. A side-mount slide screws to the cabinet side and the drawer side and needs exactly 1/2 in clearance per side; an undermount slide hooks under a drawer box built with a specific depth and notch. Mounting a side-mount slide underneath will not carry the load correctly or align, and there is no adapter that makes it equivalent.
- Are undermount slides worth the extra cost?
- For a kitchen where drawer feel matters, yes. Undermount slides hide completely so you see clean wood sides, and the Blum 563H includes integrated BLUMOTION soft-close plus 4-way adjustment to dial in reveals after install. For a garage, workshop or utility cabinet, side-mount ball-bearing slides at around $12 a pair do the same structural job.
- Do both types hold the same weight?
- In this pairing, yes - both are rated 100 lb per pair with full extension. The difference is not capacity but appearance, soft-close and how forgiving they are to install.
- Which is easier to install for a first-timer?
- Side-mount, by a wide margin. It mounts with basic clearance and is far more forgiving of a slightly imperfect drawer box. Undermount demands a precisely built box, requires separately purchased front locking devices, and comes in fixed lengths with no field trimming. Side-mount's cost is a visible 1/2 in slide on each side and no soft-close on the base model.