Johnson Level 1812-0025 StudSquared Power Tape, Black/Yellow The back of the tape has a center located V notch for marking Both sides of the tape have a unique slide rule extender guide for marking and squaring wide boards The tape body is the same dimensions as a 2 X 4 stud The measuring blade is nylon coated with large easy to read numbers Can be used as a square a 1-1/2 -Inch layout for single and a 3-Inch layout for double framing members. A Marking radius and to mark along a parallel edge