The Surveyor's Rule is a tape and tape holder combination that attaches at any height to your prism pole. NOW one person can do the job of two. Can be used to find offset line either on the ground, top of stake, or from an existing building or wall. Ideal for setting points behind obstacles, trees, posts, rock walls, etc. It compensates so the measurements are from the exact center of the pole. Will hold most 16 ft. tapes but works best with the Surveyor's Rule 18 ft. tape. The tape is of professional quality. The tape blade is 1" wide, yellow in color and marked only in 10ths/100ths. It's hard to misread. Manufactured exclusively for surveyors and engineers. Tape and holder can be purchased together or separately.