Deciding the mount type is important but more than likely it has already been decided for you by the cabinet design. There are three mount types for drawer slides: side mount drawer slides, center-mount slides, and undermount slides. When determining the most suitable mount type, you have to consider the space between the cabinet opening and the drawer box. Side-Mount Drawer slides for side mounting usually come in sets or pairs with slides for each side of the drawer. They come in either roller or ball-bearing mechanisms and require a clearance of at least 1/4″ between the sides of the cabinet opening and the slides. There are basically two types of drawer slides suitable for side mounting: telescopic extension slides and roller bearing slides. The simple two-section roller bearing slides are what you will find in the majority of kitchen cabinetry. They are cheap and widely available but they do not allow for a very long extension and their weight capacity is limited to 50 lbs. Telescopic extension slides offer any extension length you require and can hold huge amounts of weight. Firgelli heavy-duty drawer slides can carry up to 500 lbs of weight with extensions up to a whopping 60 inches. Installation of both these types of slides is pretty simple and can be done by anyone with a tape measure, screwdriver, and wood screws. Center Mount Drawer Slides are sold individually as they are under the center and lay flat. the downside of this is that the slide loses its weight capacity when turned however the benefit is that they are hidden even when open, and you only need one per drawer. They are ideal if want to keep a low capacity. required clearance will be determined by thickness style. Undermount Drawer Slides are the ball-bearing style, and they come in pairs but don't extend the full length that matches the closed length. They are mounted to the cabinet’s sides and are connected to locking devices that go on the underside of the drawer. They require less clearance, usually around 3/16″ to 1/4″ for each side, and maybe a little more work to install. If you are looking for quality slides with exceptional weight capacity and extension length, see the links below to Firgelli Automation slides.