An undermount drawer slide mounts into a groove in a drawer box. They're often identified by the height of the groove. For example, OVIS sells a 17-mm style but not a 27-mm style. The basic difference between the side and undermount slides is that side-under mounts require less space than center-under mounts. Undermounts, on the other hand, need more space between the opening of the cabinet and the drawer box.

Another major difference between an undermount and an overmount type is the amount of clearance required. An undermount drawer slide occupies space on the sides of a cabinet while taking up the entire weight of the compressed load. A telescopic type does not always open fully but does move the full length of a drawer. Aside from the added space, undermount drawer slides do not have a bearing on the underside, meaning they will likely experience problems with noise and wear over time.

Undermounts require a minimum clearance of 3 inches, while center-mount slides require a minimum of one inch of clearance. Both types of slides require the same amount of space. A side-mount slide is the better choice for cabinets with limited space. It is easy to install and provides a smooth, quiet operation. You can purchase a low-cost model, but keep in mind that it will not last as long as an over-extended drawer.

Before installing an undermount drawer slide, you need to determine the depth of the drawer box. For example, a single-drawer cabinet has a depth of about 1.5 inches. A double-wide cabinet requires a depth of three inches. If you're planning to use a full-extension undermount drawer slide, be sure to read the manufacturer's installation guide before attempting to mount the slides. This makes the process easier and less frustrating.

Undermount drawer slides require a minimum clearance of two inches. You can use any size undermount slide, as long as the drawer box is the correct depth for the undermount. A ball-bearing undermount is a little more complicated to install than a traditional undermount, but it will still save you money and make your project more functional. The best option is a combination of both features, as long as the two components fit snugly and function well.

If you are replacing a drawer slide, be sure to check the required clearance before installation. A side-mount slide will need to be mounted on the side of the drawer box. However, a front-mount slide is more likely to need a higher clearance. A top-mount slide will require additional clearance. Aside from the standard clearance, an undermount soft close drawer slide is also more expensive than a side-mount. In addition to requiring a larger space, the undermount glides are usually the most expensive types.