Abstract: A lettering guide comprises a folder includinng a strip of material, preferably plastic and transparent, folded over to provide a bottom support sheet and an overlying top hold-down sheet, and defining an upright fold edge and an adjacent upright margin area. An elongated slot of uniform height is cut through the top sheet extending to the margin area and of a length less than the width of the top sheet. The slot extends at right angles to the fold edge. A paper sheet may be snugly interposed and retained between the top and bottom sheets in registry with the fold edge. The paper sheet is adapted to be lettered in a straight line through the slot throughout its height, the line of letters extending at right angles to the fold edge. Successive lines of lettering may be applied to the paper sheet upon successive advancement thereof at right angles to said slot. The lines of lettering are all parallel, uniformly spaced and extend at right anngles to the edge of the paper sheet.