Right angle measuring device

A device designed to materialize limits perpendicular to existing or future limits, comprising a housing in the form of a right angled triangle, at least one winder guided in rotation inside the housing, at least one flexible and inelastic material divided by at least three retaining means fixed at predetermined locations, and at least three fixing means adapted to support the retaining means, the diameter of each fixing means being substantially equal to the an inside diameter of the retaining means so as to position the material along a direction perpendicular to the direction of an axis of the corresponding fixing means, the housing comprising a hole at the vertex of the right angle of the triangle to keep it in position with one of the fixing means.