Table indicates arrangement of No. 5249 sills. 12 Following the number 5249 indicates a 2-section-long sill; 13 following the number indicates a 3-section-long sill. Example: A 5-section-long greenhouse would require one 2-section sill and one 3-section sill. (5249-12 and 5249-13). Other longitudinal members such as ridge, eave, and vent header are similarly identified with either a 12 or 13 following the basic 4-digit identifying number.