The official Instant Roof plugin (now often part of the Instant Roof NUI suite) is a paid extension developed by Vali Architects
# Extrude downward for eave vec_down = Geom::Vector3d.new(0, 0, -thickness) p1_down = p1 + vec_down p2_down = p2 + vec_down instant roof plugin for sketchup free download fixed