The invention relates to a device (1) of assistance to the site installation, such as buildings of real estate of dwelling, with furniture, including/understanding : - a first element presenting on a printable surface, a first impression of the plan of the aforesaid buildings on a predetermined scale, - second elements (3) separate and distinct presenting respectively on printable surfaces, impressions of the geometries (G) of the pieces of furniture composing furniture, according to a scale identical on a plan scale of the buildings, - a support (4) ferrous/magnetized known as first element (2) interdependent of the printable surface of known as the first element (2) and supports (5) magnetized/ferrous of the aforesaid second elements (3), interdependent of printable surfaces of the aforesaid second elements (3), of such way that the aforementioned second elements (3) can be fixed, thanks to the attraction forces between the aforementioned supports magnetized/ferrous, independently and of manner repositionnable on the aforementioned first element (2).