Abstract: An apparatus comprises a housing, a clamping unit associated with the housing, a biasing system, and a length indicator. The clamping unit can be inserted through a hole in a structure into an interior of a nut that is positioned relative to a first surface of the structure. The clamping unit can engage the interior of the nut when a portion of the housing is positioned relative to a second surface of the structure. The first structure is substantially parallel to the second surface. The biasing system can bias the portion of the housing positioned relative to the second surface of the structure and the clamping unit towards each other, while the clamping unit is engaged with the interior of the nut. The length indicator can indicate a length of a bolt when the biasing system has biased the portion of the housing and the clamping unit towards each other.