3 and 4 inch letters are good for painting on curbs. 12 inch letters are customary for number and words at the entrance to a parking space. 24 inch letters are good for NO PARKING stencils. 36 inch letters are a good size for DRIVE THRU. 96 inch letters are usually used for STOP and YIELD in large parking lots, and for roadway markings like ONLY or SCHOOL XING.