The mudsill, also called a “sill plate”, is the first layer of wood to be installed on top of the foundation wall. It serves as the anchor point for theÂ home’s framing. Because the floor and walls will be built on top of it, the mudsill needs to be installed straight, level, flat, and square. In this video, master carpenter Norm Abram explains the basic tenants of a mudsill to our apprentices Carly and Erick, and then takes them through the installation process. As a start, they lay sill seal – a membrane meant to act as a capillary break between the wood and concrete. From there three continue the installation by snapping lines, straightening the anchor bolts, drilling holes and, finally, cinching the mudsill down with nuts and washers.