A device for determining tension in or on a line, including a housing mountable to a surface, an idler and a traveler sheave rotatably mounted on the housing, and a scale operatively engaged with the traveler sheave. A block and slot are provided on the housing. A spring disposed between the block and a portion of the housing is compressed when the block moves in a first direction and is released when the block moves in a second direction. The traveler sheave and an indicator are mounted on the block and move in unison therewith. The sheaves are aligned along the same plane and the block moves in a plane substantially parallel to the plane in which the sheaves are disposed. Markings are provided on the housing and the indicator aligns with one of these markings to indicate the tension applied to the line.