Undermount sinks are installed under the countertop. This is the most popular method of install and is most widely used with stone countertops. You cannot install an undermount sink in a laminate countertop. Drop-in, or topmount sinks are installed on top of the countertop. These sinks will have a lip, or ledge around the sink and can be used with stone or laminate countertops. If your sink is a drop-in / topmount sink, most of these models can also be installed undermounted. Please refer to the template included in your sink packaging. This is the guideline that your countertop fabricator will use to create the cut-out for the sink.