This precision outside corner scriber for use in forming outside corners on sheet vinyl, rubber base, and vinyl base. It scribes a line on the side of the corner that remains to be trimmed, using the opposite previously trimmed side as a guide. The guide leg has a rounded end for following the contour without scratching. The guide leg is adjustable in relation to the needle to compensate for various material thicknesses, and is held in place by a knurled steel fastener. The needle height is also adjustable for various material thicknesses.