Disclosed herein is a splint comprising an elongated rectangular flat strip of malleable metal having a width sufficient to embrace the major width of an extremity such as an arm, a leg or a finger, and of thickness insufficient to provide requisite rigidity for a splint. The strip is initially rollable or foldable into a compact package for storage or shipment. When unrolled or unfolded into flat form, for application to an injured extremity, the strip is bent manually transversely between its ends to provide two legs connected by said transversely curved area, and the legs are manually then bent or folded longitudinally approximately midway between the longitudinal edges of the legs into U-form, said longitudinal bends or folds extending from the leg ends to the opposite sides of said transversely curved connecting area into which they merge. The said manually produced longitudinal bends result in non-uniform U-shaped transverse cross sections in the legs and impart splint-serving rigidity to the legs. The non-uniform character of the longitudinal U-shaped bends in the legs produces interrupted contact surfaces which permit passage of air between the splint and skin of the extremity to which it has been applied.