An apparatus for tightening strap members comprises a buckle member having a first means for attachment to a strap and a second means for attachment to a strap. A plurality of longitudinally spaced apart pin-receiving boreholes are provided on slidably related sections of the buckle member such that the boreholes in one section have a vernier relationship with the boreholes in another section, thus permitting a boreholes to come into alignment as the sections are slid past each other at an adjustment increment which is less than the spacing between the boreholes on either section. A method is also provided for using the assembly to tightening a strap.