Abstract: An attachment for a tape measure that provides a guide for marking when moving the tape along the work piece. The attachment is in the form of a T-square with a stem part that projects at one end thereof into the tape dispensing opening of the casing for the tape measure and at the other end has an angle head part at right angles to the stem. The angle head part has a first flange that rests and slides on the surface of the work piece to be marked and a second flange at right angles thereto that engages and slides along an edge of the work piece. The flanges are turned upwardly at their ends to form a skate and tabs project from the stem to prevent lateral displacement of the tape measure on the guide during use and also serve as stops limiting penetration of the device into the tape measure casing.