Abstract: A first element may be mounted on the housing or casing of a measuring tape and a second element may be mounted on the end of the tape itself. The first element comprises a pair of pivotally attached devices, one of which is fixed to the housing. The rotatable portion of the first element includes a tape-receiving slot and a center point. When the tape is positioned in the tape-receiving slot, the center point will be located so as to fixably locate the housing at the center of a circle to be drawn. That portion of the first element fixed to the measuring tape housing includes a storage sheath for the center point. The second element is a carriage, mounted on the outer end of the tape to grip the tape at the usual holding means. The carriage includes a bore for receiving a pencil or scriber. A wedge slidably mounted in the carriage cooperates with one edge of the bore to releasably lock a marking device in place.