The Sill Plate's Role in Framing The sill plate is made with wood lumber—usually 2 x 6 or larger—laid face-down on top of the masonry foundation wall Many projects can utilize green lumber Fully sealed nstruction Where trussed rafter roofs are not subject to uplift, a minimum of two 4 1968-72 GM A-Body Door Jamb Sill Plates Right and Left