Channels that create a drainboard in a counter allow water to run off into the sink.
An optional refinement and mainly used with granite and marble counters, the decision to add runnels is a question of taste and use. With runnels, most designers insist on having the edges of the counter cover the full edge of the sink and end parallel to the inside of the sink rim. This is called a “negative” reveal — essentially none of the sink rim is revealed, or showing. This double-bowl soapstone farm sink was done that way on the sides. Since it’s pulled farther forward than usual, the front edge of the counter sits well behind the inside front of the sink rim.
Alternately, a farm sink with runnels can have a half-positive reveal. Here, the front of the counter lines up with the front of the sink and the counter extends only halfway over the rim — leaving half of it showing (a half-positive reveal) and requiring caulk, which is visible even in the photo. Some designers believe that defeats the purpose of runnels and the caulk will eventually become stained. However, this is a variation some prefer.
A Double Sink with Runnels is similar.
