A flexible printed circuit may be laminated to a metal stiffener. The stiffener may be bent to hold the flexible printed circuit in a desired position. Openings may be formed in the stiffener. Metal traces on the flexible printed circuit may be accessed through the openings. Test points in the metal traces may be accessed through the openings or components may be mounted to the metal traces on the flexible printed circuit through the openings. The stiffener may have bends. The bends may be used to shape the stiffener and flexible printed circuit to form an enclosure. The openings in the stiffener may overlap the bends or may be located away from the bends. Flexible printed circuits mounted on bent stiffeners may be used to form elongated tubes with planar sides.