Linear drains replace standard drains in walk-in showers to keep water off the floor in a walk-in or roll-in shower. This type of drainage allows for a flat shower floor with no slope to guide water to a central drain. Linear drains are a channel that runs under the shower floor covered by a grid. Water flows into the home’s drainage system. You’ll typically find a linear drain at the entrance of a walk-in shower, but then can be installed at the bottom of any wall as well.