A measuring device includes a spool mounted in a housing having opposing front and rear ends. A string is wound about the spool, and has an end is attached to a marker located outside the housing. The string winds and unwinds relative to the spool upon rotation thereof. A rocker arm, which carries a first reference mark, is pivotally attached to a support attached to the housing at the front end thereof. The rocker arm carries a second reference mark, which can be aligned with the first reference mark by pivoting the rocker arm. A brake is mounted in the housing, which moves between a first position against the spool inhibiting its rotation, and a second position away from the spool permitting its rotation. The brake is biased for movement in its first position, and a handle is provided for operating the brake.