Historic masonry walls are usually composed by external leaves of brick or block masonry infilled by rubble masonry. Structural elements made of masonry usually present extremely anisotropic mechanical properties due to the inherent heterogeneity of the system, even more three-leaf masonries. Masonry includes naturally a high volume of voids. This circumstance is emphasized in ancient masonries. Ancient masonries are usually affected by cracks and damp that increase the volume of voids and is linked to loss of strength and loss of stiffness. The insertion of rebars as connectors between the external leaves of three-leaf walls improves their behaviour in terms of strength and stiffness. Rebars are usually inserted together with grouts or mortars, thus totally or partially consolidating the internal leaf of the walls and getting better percentages of improvement. The efficiency of this technique partly depends on bond behaviour between the rebar and the hydraulic medium that covers it. Currently, bonding must be characterised by pull out test. Nevertheless, this test is aimed to typify bonding between rebars and concrete, thus omitting the distinctive features of repair and reinforcement of walls. This research team is focused on the improvement of this traditional technique of repair and consolidate walls. The first improvement got has been the optimized shape of the rebar. This paper explores the adaptation of the pull out test to the particular circumstances that affect bars that reinforce masonries. All this process, as well as the issues that arose, are described in detail in this paper.