A unitary fastening pin the design of which has flexible protrusions on the lower ⅔ of its shank (2), preferably in the shape of convergent geometrical figures (spade-shaped), molded round the longitudinal axis. The outer overall diameter of the protrusions (2) is greater than the hole into which it is to be inserted. The pin includes a flexing neck (6) between the lower shank and the head (4) and also has tapered alignment splines (16). The pin is particularly suitable for fastening threshold strips to cover floor-covering joints.