A masonry guiding tool for attachment to a backing wall, comprising a base member for attachment to the backing wall and an elbowed plumb line holder. The plumb line holder comprises an elongated mounting portion defining a first axis therealong, the mounting portion being movably carried by the base member and axially movable relative thereto along the first axis which is destined to be parallel to the backing wall. The plumb line holder also comprises an elongated plumb line support portion transversally connected to the mounting portion, the elongated plumb line support portion defining and extending along a second axis transversal to the first axis, the plumb line support portion for movably holding a plumb line. The guiding tool allows the plumb line to be movable along the first axis by axially moving the mounting portion relative to the base member, and along the second axis of the plumb line support portion by moving the plumb line along the plumb line support portion.