Abstract: A relatively thin, stiff, flat guide line holder or “trig” for accurately supporting and positioning intermediate portions of tautly stretched guide lines such as are used by bricklayers and stone masons in laying courses of bricks, blocks and stones during the erection of masonry walls has a centrally located body portion, and an integrally formed, forwardly projecting guide line support portion. During use, the body portion is positioned atop a flat surface of a wall being erected to support the line holder at a desired height to be met by masonry elements added to the wall, with the support portion projecting forwardly beyond a front surface plane of the wall being erected. Passage formations defined by the support portion open downwardly through a bottom surface of the support portion at two spaced locations along the front surface plane when the line holder is properly positioned.